@Keith Chang Jie depending on where you live "house hacking" may be the easiest first step.

Based on things she said to us in her last days, I believe my mom's wish for me and my siblings is to create generational wealth or start family businesses—which will be, in a way, her gift to the grandkids she will never get to meet.Well, my husband is pretty against the fixing/flipping/renting game, citing our inexperience and the risk involved.

It's not impossible to mix personal and business interests--I've done it with my family--but combining an "ex-spouse" relationship with a landlord/tenant relationship invites any small problem with your tenant to drag in all the personal baggage from your marriage, and any unresolved conflict from your marriage to be used as an excuse for causing trouble with your property.You clearly want to be decent and help her out, which is awesome, but a better way might be to just gift her part of a downpayment on her own place, or a certain lump sum to subsidize her rent elsewhere. 

Househacking seems to be the easiest way to get a start on building a portfolio of properties so I believe that could be part of the equation but my real question here is would it be to my benefit to pursue a real estate license? 

Google voice is the easiest, problem is it doesn't allow for mass texting.

Is the $100k a gift? 

Everyone built 10 x 20'sfor some reason and they did it at the south end of town where thezoning is easiest.

Ideally, you would like to see many comps in recent months, which would be the easiest way to find high demand areas with established renter bases.

Easiest solution is to have your lease include a clause for cleaning up after the dog with a fee if they don't. 

Having a cosigner or co-borrower would probably be the easiest route, if you can get one.