Partnering to start a REI LLC

[Nathan Shankles]

I am 32 years old, a high school teacher and I currently have two positive cash flowing rental properties that I've acquired over the last 8 years. I would like to continue to build my real estate portfolio and retire on its income in 18 years at the age of 50. Two coworkers who have collectively flipped 3 houses came to me and asked if I'd like to partner with them in starting a real estate investment LLC. Both of them have values similar to mine, although both of them are 20 years older than me. One of them has connections with wholesalers while the other has some knowledge, experience and enthusiasm. What are the 3 most valuable questions I can ask before deciding whether or not to partner with them?