How to find a company for cost segregation study?

[Whitney Griffith]

Hi, newbie question here.

I want to have a cost segregation study done this year on a STR I purchased in Missouri last month. It is currently in service, came fully furnished, and I will renovate in January.

I did a search on cost seg companies thinking I'd find one local to Branson, MO. I did not, or did not know what to look for. 

Any advice on how to find and select a company, do they have to be local? How long does a study take, I've seen a 6 week estimate online? Can the study start in 2022, but not be completed to be counted in 2022?