Then the man's wife got involved, listed it with a realtor, who said it's really worth $500K, and 3 weeks later sold for $530K.

Feels like a good deal (nice lower income neighborhood, bike paths, parks, 10 minutes from personal residence ) but the AC and roof may not have too much life left.Based on my analysis, I think the FMV for a 2/1 like this is closer to 35k.Inspection in a couple days - planning on asking for $3-5k back at closing to a) mitigate risk of roof/hvac replacement and b) bring purchase price closer to FMV.Is a deal like this worth walking away from if I don't get a concession post-inspection?

Just one of the risks of investing in real estate I suppose but hey, if their was no risk involved then everyone would be doing it and the reward would be much less. 

.), from all people that are involved in the Joint Venture.

If you are involved with contracts for construction, excellent.

There are a lot of groups that you can get involved with in terms of investing; @David Torres runs a group on Wednesday nights that you'll want to attend as he does a great job.  

I have 5 business ideas that involve real estate and giving back to the community, to decrease violence in cities I once lived like Chicago and DC. 

it seems as if option #1 allows you to quickly scale with less money (basically furniture and a security deposit) but has the downside of lower margins since you're not building equity.I've also thought of other ideas such as buying a few properties under a llc with several other investors, where the total cash per person would be the same as if you bought 1 property by yourself but it's diversified across different markets and reduced risk.

which I have noticed primarily involves something along the lines of "fear of the unknowns" or basically just to "jump in with both feet and quit making excuses".

It's just a matter of pooling people who are willing to take a risk.