Narrowing down the options will probably come down to comps and city/neighborhood specifics; things like permits.Any good suggestions for finding out how long permits are taking in certain areas?

There are only 2 options for those.

I wasn't aware it was an option.

The cash flow is a bit sub par on this one and I anticipate some larger expenditures coming my way in a year or two so I'm contemplating this as an option.

Using a HELOC for the down payment on the second home might be an option, but lenders may require you to wait a few months post-closing on the multi-family before approving new loans.The BRRRR-style approach could work if you can renovate and refinance quickly, but make sure the timeline aligns with your lender’s requirements.

If you find you are unable to raise the money for an all-cash purchase, switching gears to Fannie will only work if you have a LONG time to close in your PSA or have many extension options (which usually require more hard earnest money.)

The second son is married but has not lived in the home at any point during the last 20 years so this doesn't seem to present any options for savings.I thank everyone in advance for your thoughts. 

Fishtown and Point Breeze are strong options but can be pricey.

If you do go the seller finance route, consider asking for a right of first refusal option in the event the seller ever decides to sell the note. 

I met with Wicked Smart today and was told they help you set up a lead sourcing system, help you structure creative financing - which is essentially lease option/purchase, subject to and owner financing....all strategies I am interested in learning more about.