Partnership after closing? Can it be done?

[Brian Fabel]

We (my wife and I) had been looking for a partner to go in on a property, but couldn’t find one, so moved forward; we made an offer on a second home that we will also use for AirBnb short term rental when not using ourselves in a market 2 hours away that we visit often for recreation.

we have just closed, and now we have a friend who has offered to go in on the deal. What are some ways that we can bring him in? How can we structure? Can we do it without modifying our mortgage and just adjust ownership stake and receive his cash on the side? Do we neeed to notify the deed or can it just be drawn up with an agreement by lawyer?

Our potential partner is coming in with ~1/3 of total value in cash. We did 20% down on the close.