The 108's and 118's are lawn tractors that were released in 1972. They are identical in all respects except that the 108's had a Peerless manual trans-axle and the 118's came with a true hydrostatic rear. Both transmissions were belt driven by the 8 hp B & S vertical shaft engines they came with. Headlamps were an option. These would cut grass, plow snow or blow snow as well as tow a trailer but that's pretty much it. They are very well made units and quite collectible.
As for value, that's a toughy. I just paid $150.00 for a 107 and was happy to do it. The 107 is the model made previous to the 108. Condition is important as well as whether it's complete or not. The one I bought is complete, in nice condition and is a running tractor complete with the deck. I tried to buy a 118 from a guy and I offered him $125.00 for it. He had repainted the whole tractor some gawd-awful red and had swapped out the original engine for another Briggs. He still had the original engine but it was non-operative. He found someone to give him $180.00 and that was the end of that.
If you can pick it up for somewhere around $100.00 I think that's pretty fair for both of you.