Got a call a couple weeks or so ago from a realtor that refers me a lot of work. Said he had two addresses for me that needed prices for Roof Cleanings. Said they were for a Corporation that buy's 20-25 houses in the Houston area a month. Went out and looked at the houses and submitted my price. A week later I heard from the representative from the Corp that is buying the houses. He explained that of the 20-25 houses he was probably going to want about 1/2 of those to have the Roof Cleaned. He also stated that he had been told by some of his contractors that the cleaning of roofs was a sham and that it causes damage. After doing some research on his own he has come to the conclusion that that his contractors are probably wrong and his having me do his personal home today as a test. He will be there to watch and see how we do it and then will decide from there if he want's to proceed with the other houses. I am charging him full price today and he know's that. It's a one story easily walkable roof. He also understands that if he does come through with the anticipated 1/2 of the 20-25 houses that he buy's, and that payments in full are made as agreed upon, future consideration can be made about price or a free driveway cleaning, or cleaning front of the house as part of the roof cleaning, etc.
I do work for a few other House Flippers here in the Houston area. Doing Roof Cleaning, House Washing, and Odor Removal. Not a lot, maybe 1 or 2 a month but They all pay me on the spot when I am done.
Check the House Flipper out, do your due diligence. Ask him or her for references. And call them. Also, Seems like every time I would go out to do a bid, there would be other subs there, so I would ask them what it was like working for that Flipper. Do they pay on time? Are they nice to work with? DO they beat you up on price every time? etc etc. You can learn a lot from them.
The relationships I have had and have with realtors/flippers so far has worked out great. They pay on the spot, return my phone calls quickly when they don't answer and I theirs, and I haven't had a single one question me on price. The Good ones understand that what we do is very important to the success of them selling houses.
BUT, I PROCEED WITH CAUTION ON EVERY ONE and I check their references. You'll be surprised how much they respect you for doing that. There are some cheap low balling house flippers out there, these are the ones that don't really know what they are doing, watched to many shows on TV or books about flipping houses, etc. But there are also some very smart business people doing it too, making very good money doing it.
As for a Demo, if you think that would help you close the deal, sure. But remember she contacted you, so she already knows what you can do and a demo is probably not needed.
I agree with Riley, test the water on this one, you'll know if it doesn't feel right. Don't promise anything until you have seen them come through with what they have promised, which is houses and roofs for you to clean.