If more retailers vacate their space than those properties are at risk of losing tremendous value as it will be difficult to re-lease to a tenant that is not impacted by California's high costs to do business. 

I am very new to REI and would like to know if this is a great opportunity to buy in an up and coming area or if the residential properties will negatively impact my ability to rent out my other unit.

And there is damn good reason for it, the operational impact and expenses will eat you ALIVE! 

Your offers, how they are presented, how you communicate them, what terms are in there, the disclosures or requests you put all make an impact on how you and your offer are perceived by an agent and thus to the seller. 

Amazing how that can have an impact on our drive, passion for learning, and resolve to be financially secure, huh?

Madison was always more of a college town, so it was not impacted the same way.And MKE has a wide variety of neighborhoods with very different ptice ranges, look up Whitefish Bay or Wauwatosa, they are expensive. 

Impact of refinancing? 

Focused on high-impact improvements, we significantly increased the property's market value.

Because it's not an OTA but rather just a lead gen funnel, there is no algorithm impacted by you not approving a guest or cancelling one and no penalties.

I am confident that I would make some kind of worthwhile impact in these situations, at the least, the first time around.