There is also one big issue with your tax projection - the taxes of $280 are based on the vacant land taxes and will likely go up to ~$2000-$3000 in a year or so when the assessor catches up with you.I realize there is a 1031 involved so a real estate purchase is necessary, but you should compare your ROI to a safe yielding instrument like a 10 year T-note or AAA corporate bond yield. 

Which is the best, relatively safe Philly neighborhood for finding a potentially cash-flowing small MF (3 to 4 units)?

I really see Columbus Ohio as an extremely safe bet for the next 10-20 years.

Is vital oxide safe to use around the house undiluted?

However if it is rough and deteriorating/cracking then you might want to budget a high amount for removing it safely (which is not cheap) then residing the entire property.I'd try to negotiate the price down either way!

Are they really safe?

As someone with little capital to invest at this moment, I’m wondering if this is a reasonable (and relatively safe, depending on the deal) option to pursue even if I’m not clearing much in the way of cash flow to start. 

How it's being transacted in safely manner is between the syndication and old/new LP investors.

You should refocus on making it as a safe, conservative, get rich slowly, investor.  

I've discussed this with my real estate attorney who isn't a syndication attorney, and he seems to think that this could work, but to be safe, should be a small group without any association with my company.