Before you sink big $$$ into equipment, start looking for used batteries and learn how to take care of them. Even those deep cycle golf cart batteries are a great place to start, cheap and not so big that they'll break your back moving them.
Batteries are EASY to ruin by over/under charging, charging too fast, discharging too deep, etc. Batteries will cost you the MOST over the life of your system!
FREE batteries can be found in Telecommunications companies (cell, ILEC, CLEC and regular vendors). As a rule, they wire strings of -48VDC (4 @ 12V), and if one goes bad, they REPLACE THE WHOLE SET. We regularily throw away batteries that are 92% capacity in the industry. Most of them have never even been discharged past 5%, but are designed to last 20 years if short cycled.
Other than lightning strikes, all the rest of the components are much more hardy.