Like the poster above mentioned, you may want to spend a bit on the repairs mentioned, or you could put in the description that seller will give credit of "X" amount to take care of them post closing or similar. 

We do a soft pull on credit so no worries about a ding on your score

Your goal here should probably be about gaining leverage and not ruining someone's credit for the sake of revenge.

Particularly interested in options for upgraded insulation and boiler heating system, and any possible credits for that.

A full cash-out refi would mean giving up that low rate and likely taking on a much higher payment, which could hurt your DTI and future buying power.Instead, consider a HELOC or home equity loan on the rental.

When it comes to pulling credit and background checks, TransUnion SmartMove is a solid option for independent landlords—it’s easy to use, FCRA-compliant, and the applicant pays the fee directly.

So, do not take someone else's provided credit report. 

For residential loans, it is very uncommon to be asked to pay a commitment fee or fees upfront other than an appraisal or credit check fees. 

When you purchase I would mention your intentions to the credit union so you can get a jumpstart on what to expect later on.

Never hurts to have personal names to be added as additional insured.