It will typically last long enough that it goes out of style before it needs replacing from excess damage.  

Depending on your interest rates you may be able to get a better return on your excess money than by paying off the mortgages.

Speaking as both an investor and realtor based in FtL, these small MF are very difficult to get into at the moment due to excessively high pricing leading to negative cashflow if you plan to finance them. 

As a Property Manager in a market where many owners choose to manage on their own, I've seen several examples of owners losing their homes or properties because their tenants did not pay or caused excess damage.

While that bodes well for opportunities, the out of pocket cost would be excessively high as well.

When you buy a property, and hold a mortgage on that purchase, the excess cash you have between rents and costs is a form of profit but the short fall is NOT a loss, it's additional capital investment. 

This works reasonably well for many situations, but it can lead to issues when you happen to have a particularly wasteful tenant that uses excessive amounts of water and/or electricity.

Both me and my husband are currently working, so the excess, if we do have it, sometimes goes to one of our rental houses.

I don't think that taking out another one would be excessively risky.The market I'm in, South Carolina, is one that is landlord friendly. 

My question is will the excess funds go towards paying off the Commonweath lein?