Investment firm wants to do a rent-to-own on my property

[Jackie Sladky]

I own a townhouse for sometimes and want to rent it out and then sell before the three year mark.  An investment firm contacted me and wanted to start a rent-to-own agreement.  They will have to find a renter within 2 mos, which is easy.  I've never done this before, and if the deal works out, it will be good for us, as we'll have a buyer at the end of two and half years.  

The rental price is firm, and if we can agree on the selling price, I don't know what else to look for in the offer that this investment firm will send me.  Definitely I will have a lawyer looking at it, but I want to do some checking myself first.

Some questions to experienced members:

Would the fed consider the sell date 1) the start of the rent-to-own agreement or 2) the date that renter/buyer actually buys the property?  My reason for asking is that I do not want to lose the $500k tax exemption.

We have a loan of about $250k.  Would the lease agreement triggers a due on sale clause?  The investment banker mentioned that the tenant can/will take over paying the mortgage, but I don't really know the details yet and what is best - for me and the prospective renter/buyer.

If we don't do this rent-to-own deal, I can get a tenant in within one month.  I am not sure which way is simpler.  It seems that the rent-to-own is an easier option for us, if things work out.