Came across your post and we just started to look ourselves with the same objective of possible STR and second getaway home.

"We'll just refinance it." coming from someone paid to originate your ARM might not be the most objective advice you'll ever hear.

Some yahoos like one of the dozen or so Yardi iterations, but I don't get those folks so I'll pretend it doesn't exist.There is a whole different class of PMSs like RentReady, TenantCloud, Hemlane, etc that CAN be used to do some or all the things you'd prefer, they just won't function AS well for as long as the pro-grade PMSs listed above.So, if this is a side hustle that you'll dabble in for a while and then hop onto the next shiny object that walks by, I'd go with the cheapest or best UX/UI you can find in the second group.IF this is a business that you intend to keep getting better at and pursue with excellence then I'd cut right to the pro-grade PMS and learn to use it masterfully. 

Quantity was not an option.

No system is perfect, so don't waste your time chasing after the next shiny object.

Entire project must remain affordable so they cap the tenants rent including quantities @ 30% of the 100% of area median income. 

For example, is STR is a legitimate conditional use and nobody raised any specific concerns about your property specifically and only about an aversion to STR in general then in fact there were no specific objections to your property as a short term rental.

Build relationships there and focus on the market and not the shiny object of other markets. 

If the house needs renovation to make it "complete", and is only worth mid-$400ks after repair, then $515k sounds like you'd be overpaying.Some mitigating factors might be (1) if this is a rapidly appreciating area and that is your primary objective, or (2) you intend to live in one of the units and are willing to pay above market value because its a place you really want to live in.How does your Realtor justify their advice to offer so much over what you think the ARV is on a house that still needs work?

Metal objects in the grass you have to pick up before mowing.