I am looking at a property with a house and a mobile home on it close to water.  The mobile home has been there for probably 30 years and has since been added onto.  Both are grandfathered into being closer to water than current requirements would allow.

1. Is there a point where a mobile home is reclassified as a house if it get's added on to?  What is the rule of thumb here?

2. If I am looking to put a 3 bed 2 bath in place of the mobile home I believe I would need to consider it a remodel. What type of permits should I make sure are in place to support this activity. (I am not speaking about permitting to construct the house, I am speaking about permits existing with the mobile home, like permits for an ADU etc..) I am trying to figure out if there are permits/regulations that aren't present for a mobile home that are typical for a house that would stop me in my tracks. I am probably going to look to a pillar and post house to stay consistent with the current foundation type.

Any insight or references would be greatly appreciated!