Help with an interesting situation

[Jesse Semeyn]

Hi-

My family has an interesting situation. I am just learning more about real estate so I figured I'd crowd source all of the knowledge here to see what you guys would do. 

Our current house is under contract (full asking price in 2 days!). My mother in law owns and lives in a 4-plex. We are going to live in one of her units for a while and pay her a small rent so she's not losing money. We are moving with her for a couple of reasons. It wil save us on daycare costs and my MIL has rheumatoid arthritis. Her ability to move around and manage her property is getting worse and worse. 

Our current plan is use the profit from the sale of our house to pay down some debt and use the next year to save for a down payment. In about a year we want to buy a duplex/triplex where we can live and move our MIL in with us. This needs to be done in a year so that our daughter can be in the school district we want. We'd want our MIL with us so that we could help out as her health will begin to decline. We'd like to take over the management of her original building in exchange for living rent free with us. 

Eventually we could move out of the duplex/triplex if her condition gets worse and she needs assisted living and rent out both units.

The building my MIL is in right now will cash flow nicely when she moves out (about $900/mo). The mortgage will be paid off in 2023. 

How would you handle this situation? What am I not considering?

Thanks.