Sail area vs tonnage? Also question on sail conversions

You still haven't said where, the choice of boat that works depends on the weather an sea conditions. In a large river or a lake or near the coast in sheltered waters or possibly cruising on the ocean?

If you only move rarely and only short distances a motor might be better than sails.

And how many people will be living on board?

But for 2.5 millions you can get a big and nice cruising catamaran or "condomaran". Either sails or motored. That should be much more seaworthy and has less draft.

In case you plan to live off grid you should also consider how much solar panels and batteries you need. My own dream is to build a 40-50' solar powered trimaran with a massive amount of solar panels so it can move with 5-6 knots during the summer and is self sufficient and a floating off grid home.

 

There are many barges built as homes. You can frame a conventional house on top of a large barge.

 

Flat bottom barges can be sailed. Check out San Francisco Bay's "Alma"

Alma - San Francisco Maritime National Historical Park (U.S. National Park Service) https://www.nps.gov/safr/learn/historyculture/alma.htm