That's where you need to dig a bit deeper to see what works best for your situation, I would not be able to recommend one or the other.

Will need to dig a bit more here, but worth it. 

We are not able to drill or dig a new well for the property.

The best way to explaining this is for you to download an IRR calculator spreadsheet or build your own simple one and play around with one.For what its worth most deals I deem meeting minimal IRR standards is 13-15% but you have to dig a little deeper to uncover the real placements of cashflows and capitalization events... and then dig even deeper to verify the assumptions such as occupancy, rent increases per year, and what reversion cap rate was used.Again I don't look for IRR cause its manipulated a lot instead I look at total return on a 5 year basis.

are you talking about a slope and a walk out or daylight basement.. or a true dig a big hole basement ?

You will probably have to dig a bit to find a lender giving you 10% down.

I have understood the same from the websites like you mentioned they typically report higher because they do not dig as deep.For an accurate score you might reach out to a mortgage broker or banker and see if they will supply you with a credit report, you might have to pay $15-20 but it will be accurate.

Don't dig a financial hole for yourself using a bridge loan unless it really is only going to be a bridge.

I did a little bit of research for Connecticut and it seems you have to dig a hole (30-42") and fill it with water several times to saturate the ground.

The home was priced a good deal below FMV, which led me to dig a little more.