My Co-worker wants to invest with me

[Jo English]

Hey everyone,

I'm very new to BP (like last week new) and I'm already just so hungry and excited to have found this. 

I am interested in investing in multi-unit properties and was doing a search in my office  when my co-worker came in to chat with me. I told him I want to buy a duplex but I'm trying to figure out the best way and he just casually responded "I'll go in with you, I have 100K just sitting around" as if we were just discussing ordering sandwiches or something. Did I just find my first private lender? Oh the wheels are turning, and I want to do this the BEST way possible, but I'm not too sure where to start.

I'm looking for properties in the 200-300k range: 1.) Do I use the money as down payment and rehab costs and we split the monthly cash flow 2.) Do I just offer a ROI on his investment and keep everything in my name ...

I'm sure there are plenty more options as well, but I would like to get opinions from the group? 

Thanks for reading and happy real estating!!