Last thing I will add is I've always dreamed of building a bunch of environmentally friendly micro-homes on a piece of waterfront land around here.

@Joseph Tarallo Mark is spot on - don't take a shortcut, remove and, if necessary, remediate.We walked away from a 28 unit building a couple of years ago due to two out-of-service USTs which the vendor did not disclose (he was the one who converting the complex to natural gas, so was aware of the oil tanks) and then refused to take responsibility for them.The property remains unsold, but it looks like he is now removing the tanks.The environmental liability of having unused/old USTs is not something you want.  

Despite that, I'm savings-conscious and am living in a $950/month rental (very cheap for the upscale area of my city I live and work in), maxing out my 401(k), etc.

If not, drive around those houses to check out potential environmental factors: railroad, wires, slope, noise, neighborhood.

On the commercial buildings (5+ residential or mixed use ... we have yet to venture into retail or office) the CAP rate; location; opportunity for forced appreciation/performance improvement; financing availability/terms; building age and repair; environmental, debt coverage, etc.

I have a degree in environmental science and was once a certified license wilderness EMT.

Well, if a wholesaler is well-read, working hard, doing the right thing to get leads (e.g. mailing yellow letters, door knocking, negotiating deals), conscious of others time, willing to research their target (mentor or prospect), selective, then I'd argue they're already successful.  

One thing will be the applicable EPA and environmental issues concerning that industry.

Environmental and reclamation obligations can be enormous.

Canadians are very green conscious.