There's also a FFL method where you trade law runes for pure essence, without giving noted ess back. World 99 uses that. That way you don't actually spend much money on getting to 91, you just need 28 laws to start with. You don't make money then, but don't lose it either. That would cut the costs of getting to 91.
Agree. I've taken several breaks from Runescape and having cash is always good when getting back. The only really certain investment to increase is a rare. Just clean out your bank - sell what you can and keep essential stuff (like your favourite armour).
Tabbed bank would be great. I spend too much time searching my bank, tidying my bank, rebuying stuff I threw away, rebuying stuff I have in bank but couldn't find.