I am a real estate expert but not a contractor, not an ADU expert, and not a zoning expert. 

You plan to outperform the experts that do it for a living?

Real Estate Investment in Canada has, in recent years, been strained in terms of affordability, and other rules creating an additional barrier of entry; especially for foreign buyer.Although I am investor in Ontario and Quebec, I'm not a lawyer, nor an accountant, nor an immigration consultant, so make sure you consult with the appropriate expert for accurate information.

And yet every retirement expert tells you to sink every dollar you can afford in to these accounts. 

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On top of this if at all possible I’d recommend choosing specific neighborhoods to become an expert on as opposed to just thinking “anywhere in the San Antonio market could work”.

After this advice I feel it is much easier to invest locally where you can become a “market expert” more easily.

Most realtors are not experts in investing and do not themselves invest.

The most common is leaning on your agent for their expert advice.

For the HVAC, I'd just question if that's the correct and best way to go about it, but I'm not an expert, but certianly you won't get interest listing a unit for rent or sale without HVAC.