For your primary residence, lenders have to abide by federally required ability to repay (ATR) rules.

He could possibly put a low down on a “primary home” duplex however each subsequent duplex would require 25% down if done in the near term (assuming he sold his primary home which is the best path to accomplish his goals in my opinion).

Some lenders require it be built before June 1976 and some require it to be less than 20 years old.

But you should be able to find a 30-days notice to vacant for your state online. 

Most private lenders require either experience, or a downpayment -- and most require both. 

If you want to identify more than three replacement properties during your 45-day identification period, what are the additional requirements you must follow?

It depends on what that specific type is, how big the land is, and what the minimum size of land is required in that area.

@Charles PerkinsFor commerical real estate investment and to perhaps a lesser degree SFR investment, there are four primary required skill sets in my opinion:1.

Try online advertising, i.e.

I managed the properties myself, and was offered a job out of state that required long-term international travel.