You won't find more space for the money than a houseboat. You also won't find a boat that is more "unboat" than a houseboat.
Depending on where and how you plan to use it though they are absolutely great for their intended purpose....all one level, no steps, tons and tons of space, great for entertaining, family friendly, awesome for hanging out on the docks, etc. Pretty much they excel at everything over a regular boat except in the realm of handling.
Twins and high hp are just about necessary due to terrible, terrible handling. Most have little stern drives and gasers and they truly are the most unresponsive boats you'll pilot. Many don't leave the docks except for in ideal conditions due to the poor handling. Without the high hp it can be virtually impossible to maneuver them and you will be giving them a lot of gas to get any response. Reality is that probably 90% of boaters could get by with a houseboat. A comprimise of sorts would be the harbor master coastal with it's pointy bow or the very high end pluckebaum houseboats. On the TN River we actually have a number of houseboats that are diesel powered so they get a lot better handling. If the harbor master coastals were made more with diesels they would be just about the perfect inland river/coastal boat.
If you aren't doing the loop or serious long range cruising houseboats are a great option but don't underestimate how terribly they handle in any kind of a wind, current, etc.