Congratulations! We've also purchased a new-to-us 2006 LTV 210B last year. The house batteries are under the passenger seat and next to the basement storage in the back, on the driver side, under a black metal plate as mentioned below. The battery in front was made by Sparta and we had it replaced with an Instertate battery, same design, same features. The one in the back is a smaller battery and it serves as a back up to the main one underneath the passenger seat.
Ours is a 2005 Sprinter van made by Freightliner which Leisure Travel Vans converted in 2006.
We've travelled to Florida for the winter (1,700 miles trek) and the drive was smooth and very pleasant compared to our previous RV, a 37-foot Class A MH. Upon arriving here, the tires had been recalled by Michelin (they're 225 70 R16 (LTX M/S) tires. Boulevard Tires replaced them for free. You might want to check yours in case they were made in the same recall period. Info is available below in the thread called Tire Recall.
Enjoy your new RV.