No lease or MTM agreement with existing tenants

[Mike Robbins]

About to close on a triplex on Monday. The current tenants have no agreement in place. I’ve heard of an estoppel agreement, but how can they agree to continue terms from the last lease when there is no previous lease? Both are below market rents, one has been there 10 and 8 years. This will also be my very first rental property so any additional tips/personal experiences you might want to tell me I’m all ears! Thank you.