These mass produced deep cycle batteries probably have the lowest cost per amp*hour of any battery of its type and has become the most popular 6V battery for alternative energy powered homes. Use pairs these batteries in series for 12V configuration, sets of four for 24V and so on.
Life expectancy is from 3 to 5 years (4 to 8, if they're not abused!), assuming 250 cycles at 80% depth of discharge. Add these sets of batteries in parallel for increased amp*hours. Each set (or each battery) is rated at 225 amp*hours.