I like the idea, and I believe you have a market, but your prices are too low. More importantly it won't scale with inflation. In 10 years, that $15 will be worth around $10 but you will have all SEO links pointing to a domain that is most likely in need of change (You are stuck with a particular price with the domain name you have now).

$15 is way too low. I don't know where you are located, but you need to do some market research to figure out what you want to make per hour, how long the average project will take you, how many projects you can do a week, and what your overhead is per week (to figure overhead per project). Once you have those numbers, you will have a better price point.

Also, keep have a plan for what you want to do if there is more demand than you can support. Do you hire others? If so, will others work for that price and if so, how much do you need to make to pay them appropriately?

I hope above all you do not find my post discouraging. Instead, I hope you continue on with what you are doing, tweaking it to make is sustainable for as long as you wish to do it!