I've done it, Bird in the hand is always a good thing if the numbers are clear to begin with. I'm all about risk management though, it isn't so much about getting every possible dollar. I didn't let them see it though till demo was completed. I also didn't let the wife see it till it was mostly back together. Made the husband describe it to her. It was basically a carbon copy of what we had done a few streets over.
The buyer ended up putting in some custom upgrades that i wasn't fond of. I made them pay a non-refundable deposit for any upgrades they wanted with the full knowledge for any reason, including financing this deal falls apart, i'm keeping that deposit. I only made them give a deposit for things i didn't plan on. Like they wanted marble instead of Granite. I made them give a deposit fro the price difference on what I was going to do and the color they picked for marble. Same rule would of applied if the colors were out of the norm for paint/tile etc. Purple walls? Sure, 1500 non-refundable deposit please. They didn't change much compared to my plan, a slightly different shade of tan for the walls I didn't make them put more down for. Lots of small choices i let them do since I didn't care either way. They i think saved me time with a lot of the little stuff. I embrace free labor.
It worked out in the end. If it would of not closed with them, i was happy with how the flip came out assuming I could offset the extra improvements I didn't think made financial sense. I'm sure though things would of worked out better for me if they had no closed. Extra appeal to the next buyer. They had maybe 3000 in extra deposits?
Ran into very few of these types of situations...