I see your from MO, you might check out the government liquidators at
http://www.govliquidation.com/auction/view?auctionId=2509391&convertTo=USD
I have seen these 5kw compact diesel genies go for as little as $175 bucks. Since it's diesel, I bet you could find a way to convert it to run on Veg oil. I know it's a risk, but if it falls through and the engine is no good, you might have a good gen head. If both fall through, you have spare parts for the next one you buy. Most stories I have read people get ones that work.
I know this is a longshot, but call up your local cable, telephone, cellular phone, internet, and any other "techie" business or service in your area and ask about taking their UPS batteries off their hands when they do a upgrade or refresh. I have a couple of the guys at my local telephone company keeping an ear out for me.
Let us know what you decide to go with.
But on a side not you ask a question about how you hook the car alternator running off the briggs engine to the batteries, you bypass the battery charger and the inverter hooking it up directly to the battery. Your basically using it like how it works for your car. With an amp meter you could keep your engine running at the perfect amperage and perhaps save some fuel and your batteries at the same time by not running it at full blast. Their are different types of alternators, and if you decide to go that route ask us and we'll help you out there as well.
If you need hotwater, try and use the heat of the engine to warm up some water in an insulated 30gal barrel by using the exhaust or some copper pipe and hose touching the engine. You can supplement that by using some black hose on your roof or on a collector to get and store "extra" hot water.
For the lights, get some LEDs from an online supplier, i know some, and I'm sure others have some they use, but for 12v use. You can then run a 1-2 watt load on your 12v's when you need just some light at night.