I wanted to wait until after I'd owned the property for a year (tax purposes), but after that time, the negotiations fell through with the buyer. 

Another options is a cash out for business purpose primary through hard money. 

I am going through a similar process now,

I want to build financial independence through real estate investing.

My wife and I started two years ago, and we went through many ups and downs and lessons learned, so we are happy to help those starting out.

The idea is to create cashlow and wealth through equity and appreciation so the plan we can build few units , sell them and split profit 50/50, while I am the boots on the ground overseeing the process of building from start to finish, meanwhile the partner brings 100% of funding. 

I think you may have your understanding backwards as a very common strategy is for people to contribute to their 401(k) through their employer to get the full match, and then roll those contributions into a ROTH account at the IRS maximum per year (currently $7k).

I think that's fair, but I do feel like, eventually, buyers will start to see the value, and if the seller is willing to go through the extra trouble, they should be compensated.

Tax liens I agree on .. but notes through a very experienced vetted Broker who does it for a living is probably one of the safer investments and easiest to do. 

There are hiccups if the landlord hasn't completed their end of the paperwork or requirements through the online portal but nothing that was a crazy delay.