I'd suggest that if you are going to pursue this strategy that you focus your efforts on figuring out who you might want to invest with, conduct thorough due diligence on them, talk to references, and visit their offices...and invest with those groups directly rather than through a crowdfunding website.  

If ONE unit is vacant and both units are equal in rooms/bathroom composition, then the new owner will need to move into the vacant unit and then the owner can either evict to take the occupied property completely off the rental market (5 years off the rental market), evict to take back the occupied unit for personal use like moving in immediate family (2  years off the rental market), or they can evict given the tenant is a nuisance or conducting illegal activity (this is a harder method to evict since you have to provide evidence and have a case but if they're selling drugs and you have video footage or something, then make your moves) and there are a few other reasons for at-fault evictions. 

So far I've done comps, still working on land comps and saw one phone call conducted by my boss.

Any advice on what to look for when conducting market research to see what area are the best to find the investment proprieties?

If their renewal is long way off, you could do a spot inspection and if you find anything in disarray or that goes against the lease they signed you can order them to rectify and say random spot inspections will be conducted [with a 24 hour notice, of course]. 

I will make sure I conduct intensive screening for responsible pet owners.

I have the following clauses in my lease:Indemnification of Owner’s Agent: Resident(s) [agree/agrees] to indemnify Owner’s Agent for any liability arising before termination of this Agreement for personal injuries or property damage caused by the negligent, willful, or intentional conduct of Resident(s), [and/or] [his/her/their] guests or invitees.

I have also asked the owner to pay for said background checks as she did not conduct any and actually inherited these tenants herself.

What about their conduct?

Conduct additional research on the strategy as well.* Always be Honest, Reasonable, and Fair.