There is a great deal of battery discussion on this board and BNO. Lots of opinions (and some good information - those two things are not always the same).
Many folks will recommend the golf cart batteries at Sams as the best bang for the buck. Some will say that AGM is the best buy since you don't have to do maintenance and they have some great operating characteristics. Obviously, you will need a true deep discharge type battery. The so called marine start/deep discharge batteries will not give you good service.
I went the Sams golf cart battery route. Pretty sure they were made by Exide. I have 8 and that is pretty marginal, but I have a some pretty good loading (domestic fridg., quite a few computer type things, non-flammable lighting {could not resist Bob}). My plan was to run with these for a few years until they died. They are still going strong after about five years (the first two were during the converting and they had some bad treatment during that time).
My real reason for posting is to say that you need to protect your investment with a GOOD state-of-charge meter. I use the TriMetric by Bogart Engineering (
http://www.bogartengineering.com/). I try to never let my batteries get below 50% state-of-charge.
Trying to tell your battery state-of-charge with a simple voltmeter is not at all accurate. There are lots of technical references on the subject, but the simple explanation is that battery SOC can only be measured with a voltmeter IF the battery bank has not be charged or discharged for several hours and our systems don't operate that way. You could use a hydrometer to determine SOC but that is a real pain.
If you don't go with AGM, you will need to check the water level frequently and add DISTILLED water as needed.
If you treat any properly applied battery bank (proper type and capacity) properly, it will last many years.
Jim