are they filing tax returns jointly or "married filing separately"?

Most leases make tenants like this "jointly and severally liable" meaning they are BOTH responsible.

Thus, as I am at this point a ‘hobbyist’ and not a professional I presumed I would simply report whatever minimal profit or loss realized on this first joint flip project as pass through income.

Please make sure you vet your partner properly, I wouldn't recommend doing a joint venture or partnership with someone you don't really know. 

If you are able to connect with others who are invested (such as through this forum), perhaps a group of you could get together to file jointly, and split the cost. 

Potential outcomes include develop and hold/rent, lease to developer, and joint venture.

Section 121 Exclusion: You’re also eligible for the $500K exclusion (if filing jointly) under Section 121 since it was your primary residence for two of the last five years.

We file jointly, but I want the investing to be my business in my name.

Main thing for you is: - Have both you and your buddy talk to the same lender and get pre-approved to understand down payment options and what your combined budget would be- Decide how you want title held (joint tenancy or tenants in common) - do a google search on this to see which option is best for you guys- START SHOPPING!

Joint Ventured with a few partners to get this done.