Landhold agreement for investors

[Anton De Vries]

I am looking at expanding my new construction business. I want to offer up to investors to be able to purchase and hold land for me for a period of 6-12 months. My goal would be when I am ready to build that I would purchase the land outright from them, giving them a guaranteed return on their investment. 

My question is , how do I protect myself from them not being able to sell the land to another party? What instrument would be used to protect everyone on the deed?

Thanks for the help