After they calculate the tax equivalent yield they might hit double digits.

You could argue that because inflation is greater than the return you get on a savings account, my 100,000 is worth less and less every year.So I don't need cash flow, and as things stand now with my TSP (Government equivalent of 401k) and annuity, I should have a cash flow when I retire that will be adequate.  

This is the equivalent  of 300K loan to buy more property.

The financing we negotiated was the equivalent of 5% fixed for 30 yrs.

In fact, cash for keys is equivalent to a buy out, and unlike the court system you don't have to worry about the uncertainty if this tenant will ever leave.

., the words "full value," "full cash value," "cash value," "actual value," and "fair market value" mean the price at which a property, if exposed for sale in the open market with a reasonable time for the seller to find a purchaser, would transfer for cash or its equivalent under prevailing market conditions between parties who have knowledge of the uses to which the property may be put, both seeking to maximize their gains and neither being in a position to take advantage of the exigencies of the other.

I know this is a real estate investing app, but I'd like to explore every avenue of investing.I was wondering if there is a stock investing app the equivalent to bigger pockets.

Personally, I don't think an apartment complex is equivalent to a duplex - all things being equal, I believe a duplex is more desirable simply for being more like "a house".

I only do this for a short time, if the property is vacant.At lease signing, we both sign all the documents, they hand over all money in cash or equivalent (ABSOLUTELY no personal checks), and I hand over the keys. 

The web sites I use are: property appraisal (has links for the permits, if any), public records (has information on the owner such as mortgage, deed), permit site (has the permits, if any).I'm sure your municipality has equivalent web sites.