Need Advice on Direction for Apps

My brother suggested I should transition from graphic arts to apps. To give you an idea, this is what I'm doing now ... www.clipartillustration.com.

I realized I might actually be able to do this. I presently work in python, c++, php (for server stuff) plus I do 3d animation and modelling, python scripting etc with Blender 3d.

I'm not too confident Blender 3d would allow me to create a very marketable app, so I'm here in unity3d asking for a little direction based on the above things I do.

I'd like to make an app using my existing characters, and hopefully even use some server-side programming to keep it social and interactive, with a full on website.

What skillset should I be looking at? What about my unity 3d budget? I hope to use python or c++, plus plenty of physics, so it appears I'll be paying some money! I hope to do all of my modelling in Blender 3d of course, but everything else in unity3d.

Your answers will be much valued and appreciated.