I've been into restoration on older commercial masonry buildings in Cincinnati for years.Sense picking up couple properties over last year i have 1handy man on my team also..And can save on property management by keeping it in house.let me know some of your goals here and I can get looking.q 

Maintenance – Most likely properties will be made from concrete and masonry, so “flips” will have a very high price, but also labor and contractors are cheaper in PR compared to US, most of them are very good at what they do.

Sometimes they'll install wood framing around the installed glass block window where it meets the block wall so it gives the flush appearance when the width of the masonry is wider than the window. 

If it's an exterior masonry chimney you'll have to line it in NJ.

I assume that the city would not require any masonry? 

ALL of them are solid masonry or brick veneered, one of my basic demands for new acquisitions.

Unless I'm reading the it wrong, it sounds like these would be the appropriate code sections for the beam/girders and that in terms of sizing the engineer is correct.https://codes.iccsafe.org/public/document/IRC2015/...R404.1.9.2 - Masonry piers supporting floor girdersR602.7(1) - Girder Spans and Header Spans for Exterior Bearing WallsR602.7(2) - Girder Spans and Header Spans for Interior Bearing Walls

If you know what you're doing adding an exterior window is generally child's play in construction terms, especially if your walls are opened up and they're framed instead of masonry.

I'll take an aged port in a 200-year-old masonry wine grotto over a margarita at a tiki bar. 

I would start with porch or deck, masonry if any, and any new construction that doesn't show permits on the website..