Are there any key advantages or disadvantages to either area that I should be aware of? 

What are the disadvantages of having one boiler and one furnace for a two unit house?

Both have their advantages/disadvantages, but there’s something to be said for having a diversified retirement plan. 

What is the advantages and disadvantages for BRRRR?

Not sure if there are any disadvantages or concerns I should have about doing this.Thanks,Kyle

To be liable you must be at fault.A business entity has disadvantages, cost of maintaining the entity, legal, accounting and management.

I've done it before, there are are some advantages and disadvantages thoughif you want to close fast and hassle free, that is a spot where cash works well. one of the one's that I had bought with cash was one that needed a lot of work before it would be livable.

That's how I understand FHA mortgages work, which is a huge disadvantage.

Cash out refi will require closing costs on the entire amount so that’s a disadvantage but you didn’t say what your current interest rate is, so whether you would go to a higher or lower rate could make a difference. 

People from disadvantaged economic upbringing face this barrier more than anyone.