If your goal is to pay more for your properties, then go ahead and pay them off with that extra cash. 

I figured if this was the worst flood they saw and it rose that much building a extra 15-24 inches of concrete wouldn't be too bad. 

However, if you just want an extra property every few years, then it may be better to use the cash.

I would either collect first and last month's rent, extra security deposit, something to mitigate the risk of a marginal applicant like that as well. 

If you could convince a bank that it is worth $325k today and get a mortgage of $245 then you could write a four year lease with his full four years being paid up front (depending on laws, maybe you could even write it in a way that it is non-refundable if he decides to move early - or at least that he needs to give you 6 month notice)- then you have that cash to use for your payments and some extra that you could use for short term investments.

Spending extra time on the little details goes a long way.

It spins off dividends and mirrors the whole market so there is considerable safety as more than just a hedge against inflation.Many FIRE enthusiasts put every extra dollar they can into VTSAX and are able to retire much earlier than the average person.

If the title company doesn't want to do that extra legwork, or it isn't their company policy, or they just plain don't have the confidence for it, you can hire the services of a transaction coordinator and they will coordinate the transaction for you.If the buyer is leveraging borrowed funds for the purchase you'll have to be a lot more careful. 

Even then the cash buyers end up paying extra to secure the deal and accept lower margins.  

I wanted to give you an extra special warm welcome to the BP community!!!