Some investors I talked to are doing MTRs and STRs (this seems challenging with competing with all the other AirBnbs in CA), some are trying to do a Joint Venture and buy multi-family. 

I din't have enough capital to start on my own, so I partnered up and did a few joint ventures, sprinkled in some seller financing, and then syndicated a couple of deals, only to return to joint ventures.Pick a strategy, then a market, then start to network with all the brokers in the market. $400k is plenty to get started.Gino

You do not need a  mentor program, see if you can attend a  few meetups and then do a Joint Venture or equity deal with one of the investors there  and start from there.

Yes, you can file jointly if you or your spouse qualify as a Real Estate Professional (RE Pro) and share the benefits.To qualify as an RE Pro you must:1.

While not in TN specifically, I have assisted clients do as you have described: live in a property as a principal residence for 2 years, rent it out for 3 years, then sell.Based on the situation described, you would appear to be eligible for the MFJ joint exclusion on principle residence on your 90% share.However, in order to retain that ability, the house will very likely need to be sold (ie, sale closed, not just under contract) by the end of this month. 

I did it by househacking 2 multifamily and joint venturing on about 20 units of commercial multifamily.

If everyone is truly active, it is now a joint venture and you can have a local real estate attorney form an LLC for you (which is much less expensive).

You must work at least 750 hours per year in a qualified RE business.So most people who have high-earning W-2 jobs outside of real estate wouldn't qualify.But the unique thing about RE pro status is that even if you don’t qualify but your spouse does, you can both file jointly and claim the losses from your RE investments to offset your other active income together.

George Washington acquired a significant amount of land this way, and shortly after acquiring such created SYNDICATIONS (he later used JOINT STOCK COMPANIES when they came into existence) to raise the capital needed for development.  

Yes most definitely, however each person are able to acheive 10 maximum conventional loans, so if each properties are applied jointly, then you both would only have 10 active loans/properties instead of 20 loans (10 from each person) So you would want to strategize accordingly and see how you can acheive your maximum potentials and have multiple properties with your partner.