I would also like to refinance an STR to either increase cash flow or potentially cash out to buy another property. 

The shorter the prepayment term has an impact on increasing the rate.4.

Less buyers are attracted to these properties for a reason and they are priced accordingly.

Wondering how other investors of medium to large portfolio are dealing with this or are there any alternatives to manage increasing cost of maintenance?

Even successfully increased rents with no hassle. 

"Terminate on Sale" clauses are rarely allowed by the courts with residential leases.The good news is, many tenants don't know this.So, we always politely ask tenants to sign our lease, ask if they want to extend them and try to reasonably increase the rent.We don't recommend abusing this with strong-arm tactics.

In the long run, you will be able to sell or increase your rents. 

You could also look into installing a pump to increase the pressure in the pipes.

.: The first "strategy" I would teach you is how to leverage our money to increase your returns.

One way or another, however, the investors must work to pay down loans, increase rents and decrease expenses wherever possible.