Plus, I have my husband on board to make sacrifice in our personal living arrangements in order to get closer to financial freedom (huge score!) 

Am I able to post in the MLS without the sponsorship of a RE office? 

Question #2, If I do allow my tenant to take in a new roommate, I am thinking it best to have him set up a sublease situation with my permission so that I do not have to deal with the new renter, the current renter would be responsible for arranging all communication with them, however I would provide a lease and ensure that I am 100% comfortable with the conditions that he is setting with the new renter.

In other words, will I sell the contract to the buyer with the due diligence already done, or will the onus be on the cash buyer to arrange for this?

It really depends on the arrangement you have setup.

If I sell it and would like to do a 1031 exchange, is it within 1031 rules to live at the new property if I will also be renting a portion of the property out, similar to my current arrangement? 

In larger cities this is a pretty common arrangement, especially for large apartment buildings.

I want to make arrangements so my sister can take care of the management or sales of these properties and then transfer them to my daughter when she is a legal adult. 

A fully amortized installment arrangement.

I call the contractor, let them know what the issue is, give them the tenants contact info to arrange a convenient time, they send me a quote or if an emergency call me on the spot, I authorize the repair or get more quotes and then they email me receipt and, as prearranged, I pay by credit card over phone.