owner hold while I rehab

[Anton De Vries]

I have come across a deal that could net a nice profit, and  am a little strapped on cash as ive invested in another deal. I am looking at a house that needs around 10 - 12 k of work. The seller has had the house on the market 42 days with only one offer. here is my offer i want to make, and want to know if I can do this legally

- 10k under list

-owners take the  house off the market

- they hold the house while I invest my money to rehab

- after rehab the house is releisted with the same agent 

- at selling they get the price we agreed on and they pay their costs of that price to the REA

- at selling I pay my costs on my profit to the REA

How do I protect myself legally? I have not presented the offer yet, I want to make sure this is something I can do. Thanks for the help