Ok, this is what we got...My mom bought a condo (140k) 6 months ago with the idea of renting it and have a passive income, long strory short the HOA didn't allow her to rent it, just for her (or family) to live in, so now she is thinking about selling it again (she doesn't live in the US).She got a very good offer (170k) but I think that the market in that area is still growing because of the urban developments there (shopping mall, convention center, etc).On the other hand the apt is empty and it's costing her around $400 in HOA fees.What would you do?

At least that's what society has told me.

Is it in a location where the demand for rental properties will remain high, generally in a more core area and not part of the urban sprawl SA is experiencing?  

Cities For 2016 – Urban Land Magazine”.

I would divide my money into three categories equally.1) Flips and Urban Townhome/Rowhome/Skinny Mini Development in hot areas and lowest priced areas, but on the development structure so you pay zero for the land and don't finance your soft costs.2) 1.5% to 2% Cash flow rental properties using BRRRR in B class areas.

Some states do treat weight as a protected class and society is not yet on board with limiting the options of obese people. 

I have a degree in landscape architecture and know all about designing urban environments and landscapes.

This policy was meant to discourage urban sprawl, and made it cheaper for the City of Toronto to operate, since it could use existing infrastructure (roads, sewers, public transit, etc.) to grow, rather than need to build new infrastructure. 4 – Yearly migration to the GTA There is a greater than 100,000 person net migration to the GTA every single year.

The area has a full spectrum of neighborhoods, from super posh urban with great schools, to po dunk ghetto.

I was merely stating a problem and trying to work through the best and least costly solution, which you failed to provide.If you're going to be malicious, condescending, and rude, I recommend you create an account on Reddit.com, where the rest of society's roaches congregate to insult one another.