Oh, where to begin? Let me start with 'watered down paint'. 25-50% before the material gets to the site? Impossible. You would basically be painting with water at that point. It would be less of a hassle, and cost, to simply use proper material. You would be forced to apply three coats instead of two, as the coverage would be horrible. Whatever cost you think might be saved in materials would be lost in labor.
Over the past year I have had several jobs given to 2 Angie's list recommendations and 1 not from a recommendation. They all have one thing in common, lack of sufficient and correct preparation to save time, labor, and the fact that they put a person in charge that was a cut corners type of worker. The two from Angie's list sent worker/s back to try touch up problems, but once the job is not prepared correctly in the first place any extra work is like putting a band-aid on a dirty wound.
Research the licensing requirements for your area. These laws governing professional contractor work will be different depending on where you live. It’s important to be aware of these laws and what they mean from the outset. Contact the licensing board for your state or district to find out more about what you’ll need to do to get your business off the ground.
Yes the pricing does change, and quite significantly. I have worked inside the paint industry on counter sales outside sales and application for over 10 years. One thing many people do not understand is, the resins in the paint are more expensive to produce the higher the sheen goes. Therefore the company is at of higher cost making the paint, which in terms they charge more for the paint. I have seen a 15$ variance between flat-semi-gloss it is not uncommon and is not unrealistic to pay more for a higher sheen. Another thing to add is when doing samples on your wall prior to a painter coming is a good idea, however do not do them in huge squares with heavy coats, remember you are just wanting an idea. A lot of times the issue comes up of the paint not covering the sample coats, in fact it is covering quite well, however the paint sample applied is often times much darker than the wall color, creating a contrasting difference from the lighter surrounding wall and the sample placed on the wall. I recommend getting a piece of sheet rock and using it for the samples so you can move around with it etc.
So why not just paint your own home. I'm not a painter, so my wife and I take our time, buying the paint and supplies, and doing our own painting. Yes, we need to tape, and it's not perfect, but we get the satisfaction of seeing our completed work. Get the supplies, sliders for your furniture, and patience and go for it. That way YOU have control over the entire project.
When I had my interior painting done, after clearing out all of the furniture, myself, I also removed all of the wall plates in all the rooms to be painted. They were a beige color and probably yellowed. The wall was originally an off white and I had it painted a light-mid grey, so those wall plates would look terrible. After pricing replacement plates, switches and outlets (Would have been way too expensive to replace all of them), I decided to just paint all of the wall plates, switches and outlets (Used just a black gloss spray paint). I sprayed the plates outside and used a small brush on the switches and outlets. It worked out just fine and the blacks plates, etc compliment the wall color. It has been 7 years and the plates, switches, outlets are holding up well.