My REI holding company is a corporation (S-corp) registered in the State of Maine (where I currently reside). Under the holding company, I have two LLC's and one non-profit corporation. One LLC (taxable) I have registered in Maine with each Maine property held in a separate Trust - I concentrate primarily on single-family residential in the coastal communities of North Yarmouth, Cumberland, Yarmouth, Falmouth, Portland, South Portland, & Cape Elizabeth.
The other LLC and the non-profit corporation I have registered in New York State (where I was born/raised). I use the non-profit corporation (non-taxable) for purchasing & rehabilitating properties within the historical district's of Albany, NY for both educational/culteral and affordable-housing purposes. The LLC (taxable) registered in NYS also holds each property in a separate Trust - these REI's are primarily single-family residential concentrated north of Albany in Colonie, NY north of Siena College and south of Route 2 (an area where my mom's Witbeck ancestors lived in the early-mid 1700's).
I pursue my REI part-time, since I work full-time (utility financial analyst) & am married with two young children.