How about a boat loan, rather than a liveaboard
I had talked with the folks at the credit union. They didn't care about liveaboard or not. To them it was a boat loan. The credit/income requirements were about the same as for a house mortgage. The credit union required a survey
and appraisal by a NAMS/SAMS surveyor
and required insurance
for liability and replacement. Interest rates were about 2% higher and the life of the loan was much shorter than a home mortgage loan. (They were amused about a loan for a sailboat. Don't know what they would have thought about a loan for a custom-built sailboat.)
If I had really wanted a boat loan, I'd have shopped Boatus or Essex orů for a better rate. It would seem that requirements for a regular boat loan (the comps for value) might be less strict than for a liveaboard mortgage. Though this is confusing since Dodd Frank did exclude RVs and boats from certain requirements for mortgages.
If you get a boat loan, and that boat is your primary or secondary residence, IRS allows itemized deduction of the loan interest.