It may be unreasonable to think that they have to pay for it.

what would be the justification for paying that much?

I'm thinking if I ask the tenant to pay the other half, I'll probably need to make an amendment to the lease to reflect that.

I noticed that the previous owner let them pay half the security deposit and the other half later, which is a red flag.

When someone wants to send you a referral privately, they are probably sending you a friend that pays them a referral fee.

Pay off debt .

Suggesting to them buying their house for a wholesale range offer or lower dependent on the extent of the rehab, then having a contract in place that gives them a percentage of the profit to help get them back on their feet, paying off debts etc.

I have spoken with them a few times, they are unconcerned, and happy to have me just pay the interest every month until it converts.

People in 1981/1982 were angry they were paying 18% interest.

This is the first time I have done something like this, where it was for other reasons besides not paying rent.