There is actually NO federally mandated requirements for embryo 'adoptions'. You do NOT have to have a home study done. The home study is done if you choose to pay an agency to locate embryos for you.
You can call your local fertility clinics and ask if there are any 'donated embryos'. The clinic then usually has a protocol to have the FET done there (the clinic in NY has a donor program that cost $4,000 TOTAL (transfer & embryos included). It is illegal to 'sell' embryos (like it is illegal to sell children). Agencies can charge you high 'fees' for footwork you can do yourself (if need be). You also can find infertility clinics in your area that can ship in donated embryos from other clinics. There can be long waiting lists for donated embryos.
Also, frozen embryos certainly run the risk of not surviving the thaw. That is something you will want to consider when using an agency. If you adopt 5 embryos and none survive thaw, do you have any other options... etc.
The embryo grading system is very important when choosing embryos as there were different methods used in previous years. Some agencies will offer embryos frozen prior to certain dates at a discount because the survival rate after thaw is low.
I hope this helps. I am in the same boat. This is the info I have gathered in part of my journey.