Microstock is a tough business for commercial illustrators, no doubt, but also a market in which one can strive and have as a bridge to more advanced projects. Let’s see the pros and cons of this venue:

Let’s delve into each item:

Pros

It allows you to work from home at your own pace: Needless to say, avoiding commuting is a great benefit in itself. Be it driving back home on a dark, snowy evening or bracing yourself in the subway wishing they had air-conditioners, you are always better off without it. There is also the advantage of not succumbing to office pressure, etiquette and schedule. Be advised though, working from home is not for everyone! It is easy to fall for procrastination, sedentarism and even depression. In order to fight those you need discipline, exercise and a life outside the house. For those with kids, privacy and tranquility to work at home might be a challenge as well.

Low initial investment: With a reasonably decent internet connection (starting at US$35/month?), a US$600 computer (the more, the merrier) and a US$300 license for Adobe Illustrator CS4 or CorelDRAW! or even the free, open source, Inkscape (there are other vector based drawing programs out there, do your homework!) you can start to bring your concepts to design and your ambitions to success. As everything else in life, this is twofold. Vector drawing doesn’t require you to buy US$3K computers or US$5K digital cameras or even build a studio for that matter, but sooner than later you will be looking around for a nice (Wacom) tablet, a faster computer (maybe even beyond the $3K level) and other goodies… A quick look around (guilty as charged!) reminds me of a much more elaborate scenario including a high-end workstation computer, a server computer, a fully equipped desktop computer for those times when you need assistance, large monitors, tablets, remote backup devices, fine quality printer, notebook with portable tablet (useful if you have local clients or if you "need" to do some drawing in a café just to prove yourself you’re still part of society…), routers, hubs, OS licenses, software licenses… well, you got the picture. Again, even if you might end up with an expensive setup, remember you still only need a little bit to get started and grow along your business.

Possibility of lifetime earnings from copyright:
Well, this is not exactly illustration’s only (or microstock exclusively, for that matter) but I always savor when I check the sales reports and realize that an unpretentious image I did two years ago is still a strong seller. I am very akin to the whole copyright concept (without radicalism!), so if you are as well, making a living out of it can be very rewarding.

Opportunity to get commissioned work and Rights Managed:
Once you start to get more visibility, especially if you develop an identifiable style, you can count on all sorts of inquiries, most for work-for-hire (not my cup of tea) but some for Rights Managed as well. If you spend the time and dedicate the energy, chances are you will be able to convert some work-for-hire inquiries into Rights Managed work, but before that you need to do your own homework and truly understand the differences between Royalty Free and Rights Managed. Most times what the client really needs is exclusivity, not ownership.

Cons

You must keep a crazy pace to project your work beyond the great majority:
If you want to rise above the crowd of hundreds of thousands of self-entitled "artists" from all over the world and get your work noticed, you are going to have to work an hectic schedule. If you are currently working on a regular job and have microstock as a side business that you want to turn into your sole and main source of income, then you’re in for some pretty crazy hours… The sacred word here is visibility, but that only makes sense if you are backed by quality work and quality work takes time, which goes against the basis of microstock visibility: volume through constant uploading. There you go! Now you’ve gone full circle, better yet, spiral in this crazy rhythm. "The salvation?", you ask me. Well… balance. Balance between quality and quantity to allow for continuous visibility.

Impossible to track down correct licensing: Different microstock sites have different licensing policies, if not brutally different at least different in terms of run limits granted to the final clients. Files are downloaded on a daily basis under all sorts of licenses but who’s to say the chosen licenses are the correct ones for each case to begin with? Even if there were a mechanism to allow for usage tracking, what would you spend your time on? Creating new artwork or tracking down thousands of monthly downloads? Welcome to the world of microstock images! If you want to have your copyrights respected, you better start respecting other people’s/companies’ copyright as well. There has to be a certain degree of good faith, otherwise you’re better off seeking employment somewhere.

Deal with services created around photography, not illustration: Once the set is ready, the subjects properly prepped and the equipment ready to go, a photographer can shoot 15+ ultra hi-res RAW pictures in a single second (granted he or she has a top of the line camera and memory card). Sometimes a blank canvas will stare at you for many long hours but don’t expect that or any other specificity of creating commercial illustrations to be really accounted for by the microstock companies you will be working with on a regular basis. Make no mistake, the microstock industry is built around photography and is now adjusting to accommodate video as well. Illustrations and audio (to a certain extent) are not their darlings, so get ready to deal with ridiculous constraints, among which my pet peeve is the requirement to maintain compatibility with EPS version 8. In other words, we all are current with our browsers, our Flash Player, our QuickTime Player, we are all purchasing microstock from our smart phones but somehow we got stuck in 1998 in regards to vectors! Go figure…

Extremely easy to copycat: Truth is a vector drawing program is not like rocket science to master: a little bit of diligence and curiosity will suffice. If your work starts to get some notoriety due to embarked creativity, style and overall quality you will eventually end up in the top roster and once that happens all the lurkers eager for downloads will immediately (and I mean that, immediately!) start copying your style, your colors, your idea, your work. That’s inevitable. So the success you have worked so hard to achieve is copied in minutes by several unscrupulous "artists"? Yes! For those in the business it is not really hard to identify such people, all you have to do is check their portfolio for a total lack of one single and clear style. Their ports look like a flea market, even if the individual designs are technically correct and good quality. Besides the competition copying your work, there are the clients who every so often take unethical paths as well. Sometimes they download your file under the cheapest license but use them for commercial projects they are not covered for. Other times third party vendors do some basic editing of your files, such as repositioning elements and changing colors and then release products (and receive awards!! trust me) for *their* designs. Oh… and there is also the thieves who download the cheapest of licenses, get the files, claim they are not satisfied and "return" their purchase for a refund (promising they will delete the files from their computers) to later just use the images in commercial products without the slightest retouch. Yes, that is how low it can get, so if you’re not ready for some good doses of frustration, you better shape up!

Unstable approval and pricing policies:
Again this is not an illustration only issue, but you must get ready to deal with reviewers’ instability all the same. Once you submit an image to a microstock site, the engine starts to run. This means that being the company a microstock (emphasis on "micro") site, it has to make do with the resources they have and more often than not the reviewer evaluating your image is likely less trained, experienced or qualified than you. He or she must also be having a bad hair day… whatever reason, you will end up with an image being approved while other gets rejected. One of your best-selling images in one site will never get past approval in the other. You submit a batch including two identical images in different color ways and one will be designated a price tag of 15 credits while the other gets just one. So on and so forth. Get in the spirits of managing exceptions.

Longer time prepping and uploading files: Once a bitmap image is ready, quality-wise, it is, well… ready. Once a vector image is ready, quality-wise, well… there comes the time for technical adjustments. Certain sites have particular requirements regarding formats, paths, versions, file sizes, even layering. Some sites demand that you prove your drawing is original by requiring copies of sketches and hand drawings (even if you created the whole thing digitally). Then, there is the fact that illustrators have to upload two files for each image, a vector file and a jpeg file (for IPTC and preview requirements), which most times turn into three files for each design since you must generate a .zip file of the two. All these different requirements forces you to end up with several different files and versions of the same design just so you abide by each microstock site’s rules. This is not only cumbersome but extremely time consuming.

In a nutshell, this is it boys and girls: the illustration microstock market. Now answer me this: Are you in or are you out?