At what point do I start to worry?

[Alterego]

I was thinking I'd start with FOWLR and slowly upgrade to a reef. I was leaning towards a 90Gal with a 30Gal sump but then it dawned on me that the neighbours probably didn't want their floor to start cratering towards my side of the duplex. I would like to put it on the inside wall (shared wall), and as for space, I coulg fit a tank up to 6' long in that area but I think that would definetly be overdoing my weight limit. Thanks again.

Brendan