Need help with LTO in Texas

I am familiar with LTP but haven’t done one yet. Here is the situation: Have one of my rental properties leased out and the tenant now wants to purchase, how do I go with this since I want to keep the tax benefits and I don’t want to transfer deed. Texas is a complicated state when it comes to real Estate and you have to know your way around this so I AM SEEKING HELP from all the experts in this matter. There is a mortgage still on the property and a new law that says that this can’t not be extended for more than 3 years but my? Is can I re-extend the terms if my tenant is not qualify after the 3rd year asking for another option fee? What are the legal implications of this? How much a fair fee will be? Do I set the price of the property now or do I establish sales price on the contract at the time of purchase for the current market value after the 3rd year?

If any of you have a generic contract that can be used for this purpose I will appreciate it. I can have this reviewed and notarized but I found another investor wanting to walk me thru this and charge me the lovely sum of $3700 and I have to say NO!, that was a little exaggerated.

Thanks in advance