one other reason you should consider is the setback.

most old house are grandfather down with small setbacks, if you tear down the wall, you need to follow the new rule.

for example, water front properties usually have very small lot, to keep the same setback on water front and neighbor side, you need to keep all 4 corners the old house, because old setback is 5 feet on each side and 15ft water front, new rule is 15 ft on each side and 35 ft water front.