$350 is very reasonable for someone with your programming skills!
Since I am flexible with regard to time, how about this:
Let's make the completion date relatively long--14 days--so you can work on this project at a rate that is convenient for you, or work on other jobs at the same time if you wish.
And of course, I'll pay the 50% milestone immediately upon acceptance.
In exchange, let's set the cost to 80% of $350 = $280.
This way I can compensate you fairly while conserving some money for the future expenses/hires (Google Adwords, SEO optimization, etc.)
If that sounds reasonable, you can accept the project and I'll send the first milestone.