I was a painting contractor for many years and never asked for a deposit upfront. A good contractor should have great credit with his suppliers and an even better contract if the deal should go south before the job is done. Get to know your customer and explain how each paint covers so they understand fully before you have to apply 3 or 4 coats. If you didn't bid your job right and the client has already signed the contract then that is on you not the client. Yes I haven had to eat the difference but the client was happy and a return customer for years so I made up for it.
Filling gaps with a paintable acrylic-latex caulk cuts down on drafts and makes your trim look better than new. The secret to using caulk is to cut the tip smaller than you think it should be; too much caulk makes a mess. Also, instead of using a nail to break the inner seal, use a small wire so you don't stretch out the nozzle. Also consider buying a dripless caulk gun, which will automatically back off the pressure after each pull on the trigger to prevent unwanted oozing.
Just like with roller paint application, painters are not limited to using just one stroke when cutting in. It is important, however, to work towards the edge of the corners applying even pressure. If time permits, painters should allow their cut in work to dry completely before applying paint with rollers, keeping in mind that light touchups on corners and edges will always be required at the end.
Maybe you've just moved into a new home, and you haven't got around to buying brushes and rollers yet. Perhaps you're worried that your brush-skills aren't that good, and you won't achieve that professional-looking finish that you’re really going for. Handy professionals will turn up with everything they need to get the job done, from ladders and brushes, to rollers and tarps. You just have to provide the interior paint and primer!
His team is very meticulous, very careful, very clean, and very courteous! They're also very accommodating. For instance, I mentioned a couple spots under some angled siding where I thought a little extra filling was needed, and they obliged without question. Same thing with a request for a stain-proof primer under a balcony. Doing these kinds of little things without question or extra charges is really nice!