Primer Not Sticking To Wall?

My wife and I are really into finding free or extremely low priced furniture and painting it then reselling. I I don't want to get the reputation for having low quality pieces so I need come advice. I've sprayed latex paint which doesn't seem like a very durable finish. I've used spray paint in an aerosol can which works pretty well but is expensive and takes more time. I suppose you can thin oil paint and spray it but I've only brushed it and it is far superior than the others. totally durable and amazing. The thing with oil paint is that it is a pain in the butt to clean up, and I assume cleaning a sprayer would really suck. So, I came up with this plan to cheat. use flat latex paint and spray poly on top. sound legit? Any advice would be great. We are trying to increase our production and we want to do it as efficiently as possible, inexpensively as possible and, we don't want to have to sacrifice quality. GEEZ! we just want everything!:D

Hey Guys - I have read a lot about the problems that exist with paint peeling off walls, and I think the problem I have is that there is drywall dust on the wall from the original build. But I wanted to run it by you guys anyways and see what I can do from here. The walls had two coats of paint, it looked like a pink-beige and then a green which was when we moved in. It doesn't look like any primer was used. Our painter said that going over the area with primer would bond through the old stuff and into the wall, and he used Zinsser 123 primer. He then topcoated with Sherwin Williams 400, two coats. It's now peeling off like one giant rubber sheet as shown. [ATTACH]19396[/ATTACH] The colours are way off, it's a bright blue, with orange sticking to the walls and orange and green on the peeling parts. There is a bit of drywall dust when you run your finger along the sanded joints, and the old paint seems to adhere where the was no joint compound. What's our option at this point, with so many layers of paint on there? Thanks so much! Lee