I have not used that particular firm either, so I cannot speak to them, but here is how I would think about picking one. There is no IRS rule requiring a licensed engineer or a site visit, so nobody can tell you a study is automatically invalid based on who prepared it. What matters is whether it is defensible. A solid study inspects the property, pulls the actual construction or closing documents, classifies the assets with real cost support behind them, explains its methodology, handles indirect costs, and reconciles back to actual project costs or, on an acquisition, to the purchase price properly allocated after backing out land. Cheap online or questionnaire only studies tend to get thin in exactly those spots, and since the burden of substantiating your basis and classifications sits with you rather than the provider, that is where it costs you if it ever gets examined. Practically, I would ask any provider for a sample deliverable on a property similar to yours and check whether those pieces are actually in there before you look at price at all. Whether a study makes sense for your building comes down to your own facts, so run it by your CPA or tax advisor before you commit.