Offer the new lease first, within whatever legal requirements are dictated by their current contract and your local law, and see what happens.

Thus, the only document in question is the original sales contract, which dictates how the deposit (not the assignment fee) should be disbursed.You probably should have spent a few hundred bucks to have an attorney draft a solid assignment of contract (a one time cost for a document you could use repeatedly).

Now, the type of tenants will also dictate how much work you will have to put in to maintain the unit.  

I don't analyze properties...I analyze Markets based on a financial profile dictated to me by my REI/Business Plan.  

The market dictates the prices.

If you don't need the money and you bring them in during construction after alot of the soft costs are paid then you have more control because you took the "risk" and have more power to dictate how the returns can work.  

Supply and demand dictates that this drives the prices up, many times past the point of actual value.

This dictates not only the amount of time you can list the property, but also you may have to pay them after your contract expires if you sell it within x months.Call the broker and present your case.  

Rich conveys marketable title to Bill, "except and subject to the lien interest in favor of XYZ Bank, shown in the Office of the Recorder of Deed public of Tin Cup County, RC, in Book 123, at Page 321".For a contract, "title taken by buyer subject to the existing mortgage having an approximate balance of $33,333.33 in favor of XYZ Bank" .....usually acceptable unless state law dictates specific language.     

Don't let them dictate to you what they want to do.