Its a funny thing, but most states have a "department of motor vehicles" and a "tax department" and whatever they are called, they usually can be found on the web. They also usually post FAQs that tell you what is subject to registration and tax, and usually treat a boat as a "motor vehicle" as long as there is a primary or auxiliary engine permanently installed on it.
Most states require local registration after some period ranging from 90-180 days, and if you sign a marina contract for a period longer than that, you can bet the local tax authorities will take that as proof that you need to register the boat there.
Do your homework, check the states where you think you might keep the boat.
And don't even think about offshore titling for it. That would make the boat a "foreigner" and you'd have to get a US Cruising Permit for it--and take the boat out of the US at least once per year. That's just where the fun would begin.