You have a couple of rooms to get painted. And its just paint on the walls right? I mean, how hard can it be? You get 3 quotes and go with the cheapest. Because each of the 3 painters are essentially going to do the same work, aren't they?
There are basically two scams that very cheap painters use to turn low bids into gold for them and garbage for you.
The first way is to simply skimp - on labour, preparation and materials.
Cheap paint is lot cheaper than good paint. It looks fine going on but will literally rub off on your hand when dry.
Watered down paint could start out as quality paint but by adding water it magically becomes half price paint. It too is hard to spot until its too late. Its also thin and transparent and may need extra coats (and extra money from you - see below).
Another way to skimp is to rush through the job. Sure paint goes on the wall but it also splashes onto your floor, furniture and dog.
And rushed paint work is usually laid over improperly prepared surfaces. So it peels or flakes off later.
The second way is Bait and Switch. But in the trade it's simply called 'Extras'. You find out after the job starts that what you thought were included are actually extras - very expensive extras.
Usually the painter comes to you with the sad news that, now he's started and taken your deposit, things are harder than first thought. Maybe the walls or ceiling need patching, that wasn't included in the quote. Or the colour you chose needs a special under coat that wasn't included in the quote. Or the kitchen walls need to be scrubbed of oil, that wasn't included in the quote.
Any of these Extras should have been recognised at quoting stage, talked about and included in the quote.
The way to avoid most scams is to demand a fixed, detailed, written quote agreed BEFORE the painter starts. The quote should outline what is going to happen to every surface, what paint will be used, how many coats etc. Beware of micro type disclaimers about unforeseen issues. (The fencing industry are very good at finding expensive unforeseen rock to dig up at your expense!)
You shouldn't need to pay a deposit either. Any business that is that short of cash, should be avoided.
And finally, you really do get what you pay for. Most tradie horror stories or total rip offs come from a guy who is pretty obviously dodgy but we go with because he was ... cheap.
I've been drawing and painting since I was a kid. I've studied art and design and have worked in visual areas my whole life. Now I'm a house painter!