I'd hate to dig a deeper hole than the one they already have.

My reasoning:-There are other deals out there way better than this one, you just have to dig a little to find them. 

Dig a trench and lay pipe.  

The tenant will also forget what amount they paid and you will have to keep reminding them.You have to keep them at 30 days for their own good or they will dig a hole intentional or otherwise that they can now not get out of.

It appears we are on the right track, just need to dig a little deeper.

Best Regards,ColtonTry DIG as mentioned earlier by @Joseph Scorese.

In todays current society of eviction moratoriums, stimulus checks, rampant unemployment, and deadbeat tenants, would I be willing to dig a little deeper into his screening if I was 100% guaranteed to get my money in full? 

@Ma Diga sorry to hear you have had a year of vacancy.

I would assume you are a full time investor. i would love to dig a little deeper and hear some more about what kinds of systems you have in place to steadily buy 4-5 homes a month.

have you considered abandoning the basement . as in  reposition the furnace upstairs. line the basement with a waterroof membrain then fill it in . its a drastic solution but if you have that much ground water your running out of options .a cheaper fix would be to dig a sump about 2 feet deep and get one good sump pump  this would stop the water getting upto the basement floor so youd be dryer but your future will be forever connected to that pump