Renting With Option To Buy After Buyers House Is Sold
I currently have a house for sale and and have an interested buyer. She has asked it I would be interested in renting to her until her house is sold, thus allowing her to buy. My question is how should one go about it? 
Even better than a lease with option to buy is a contract for deed or land contract (same thing). Either is very simple to do.
Under a lease option, you sign a regular lease where you get a security deposit and montly rent. You also sign an option to buy wihch gives your new tenant the right to buy your house at X price within Y period of time. You receive an option deposit (preferably several thousand dollars) which is applied to the purchase should they decide to purchase but is non-refundable if they don't buy your house. Let me point in that using this method, your tenants have the OPTION to buy.
If you use land contract it is also very easy. You basically collect a down payment (several thousand dollars preferably) and then amortize the balance and you receive so many monthly payments until a balloon date if you wish. You could have the balloon date in 6 months in this case.
Either way would probably work and I'm not sure which way would be better. The main thing I would say is to collect a large enough down payment or option deposit to carry you through the winter (I don't know where you are) should your buyer not come through.
You need to have a plan if the this person doesn't end up buying.
Write a short term lease option agreement. If she really wants to buy the property she should be willing to make a significant option downpayment. Don't get locked into a long term contingency period unless your getting enough option money to cover your expenses during the contingency period. I'd also make it a short term option.
Have you thought about trading houses with her? Taking each others notes subject to and working out the equity difference. Might be a good way to get a house at a reduced price and get yourself a decent rental property.
If she really wants to buy, let her sign a lease/purchase instead of a lease/option. The l/p will force her to buy instead of allowing her to buy. This will protect you in case she is just looking to be a short term renter.
If you collect a nonrefundable Option Consideration payment, you may not care if she buys or not. Lease Purchase Agreements are usually one Contract. That might create an equitable interest, forcing you to foreclose if there's a problem (as opposed to just a standard eviction). Just my opinion, but I would try to collect 5 percent up-front and use a Lease Option.