The college girls are very sweet. 2 play sports on scholarship and work and have told me they pay their own way with their scholarship money, loans, work etc and have good references from previous landlord and credit score. 

It’s difficult to get a line of credit on an investment propertyI would just get a PM and pay them to manage it.

To estimate offer price after showing, do you know what are the things to pay attention to look?

This money can used by the Landlord to pay their mortgage, set away reserves for structural and roof capital expenditures and most importantly, put money into their pocket.

Are points worthwhile paying, depends on your plans.

It can be done but you need to pay close attention to current home and new home.

My concern is the investment in Detroit would need to create high paying jobs in the city and those earners to live in the city for change to come at a granular level and be sustained.

I only recommend using a HELOC for scenarios where you'd be able to pay it back within a year.Alternatively, you can just buy another investment property with lower down payment, which is a better interest rate than anything you'll get on a 2nd lien HELOC/HELOAN. 

Another thought - When purchasing HVACs, roofs, tree removal, siding, etc. you can very easily pay "retail" (just look for the biggest ad campaigns online) or you can save 30-50% by being your own GC and finding or going to the crews directly.

So it would not make much sense to put only 15% down if you have to pay an additional 4.125% in points to make it happen.