Check out my cousin's bus-rebuild blog:
www.beginningfromthismorning.com. They're completely renovating a '64 GM bus and plan on it being all-electric, except for water heater and back-up furnace. Bought 8 435w used commercial solar panels and a '13 Nissan Leaf battery. About 3,400w of PV generation and about 3,200 amp hours of battery storage. Yes, it was way more than your budget, but it's also a cool idea. There are people buying up electric car batteries to make backup storage for their houses.
Personally, my needs are =way= less, so I'm thinking of =one= similar panel and 7 Nissan modules, for 435w of generation and 460+ amp hours storage; more than double my 2 6v golf cart batteries. Cool thing is that I can do this in stages. Add one battery first and just charge off the house charger. Add solar later on. Maybe add a second 7-module battery. Yes, the battery would be 48v, so I'd have to add a step-down transformer, but that's pretty easy.
As far as being illegal to have solar while on the grid, make your "solar generator" temporary with an INPUT plug into the panel then, after the emergency is over, simply unplug your "generator" and you're no longer connected. I =seriously= doubt the power company is going to come 'round to see what you're up to. Frankly, it'd be no different than if you'd wired in a gas generator, IMO.
Lyle