I guess it depends on your risk tolerance and your ability to find a better deal than the one you already have with the equity you are pulling out.

Depends on your goals.

Depends on how old they are - kind of hard to tell from your picture.

@Robert FrazierThis really depends on the market. 

Common utilities paid by the landlord will be similar if not the same; standard services (extermination, changing filters, snow removal, fire safety inspections etc.) will cost the same.Expenses will vary depending on the market.

It depends on a variety of factors. 

It all depends on if you want more cash flow now or to have no mortgage sooner.

It can do better or worse depending where you are, but these are some general ideas of what you can get out of it.

Depending on where you are looking, inventory for 1-4 units can be a challenge as a lot of the NW suburbs are all single family homes unless you are further NW like Rockford or Elgin or something like that. 

You can expect to pay about $5k per year or so, depending on where your unit is and how much you pay for it.I can give you more accurate details and help run numbers on your unit with you, if you like.