Buying a can of premium paint, then bait and switch over to low-line products? Again, complete nonsense. Think about it for a moment; the Painter needs 5 gallons of wall finish. So, he buys one can of premium and the rest 'cheap'? How is he going to hide the 4 other gallons? What's he going to hide it in??? He only has ONE gallon of premium. It's not as though he's going to keep older can labels, they would be covered in paint of a different colour.
Remember: You want to get the highest quality paint your budget will allow to ensure its lasting beauty. You'll also need painting supplies like primer, brushes, rollers and painter's tape. A professional will have these items on-hand. According to statistics, paint and other supplies account for about 15 percent of a professional painter's total cost; labor will factor into 85 percent of their charges.
If you do decide to make it a full-time business, the sky’s the limit. The house flipper/contractor that I worked for billed clients $35 per hour for painting, and paid his best painters perhaps half of that, so there is room for some profit there. Consider the case of Matt Shoup, who started with $100 and went door-to-door, asking neighbors if they needed some painting done, then built a painting business that earns $2.5 million per year!
For interior paint I prefer the semi-gloss, provides a very subtle sheen and is super easy to clean -no flaking, chipping, etc. I've painted a lot, and found that Sherwin Williams Ovation paint has been the easiest to use, and provides the best coverage. I even painted my ceilings with it and WOW! I was done it no time at all, with perfect coverage.