Avoid the private REITs and buy one that's publicly traded. Also avoid mortgage REITs, those lend money (vs owning buildings).
Here's a simple screen for office REITs with a market cap over $300m on the NYSE (note that there are other types residential/retail/medical/etc under the "industry" filter):
https://finviz.com/screener.ashx?v=111&f=cap_smallover,exch_...