Oh......a dealer........are you going to be Ebay.......internet or a fullservice shop? Iwould say....... not a ton of hop ups for them I would think any of the 8E line and the 1/5th scale gas and electric are popular and they even have planes!! the parts are so cheap I would think $20-30000 of parts inventory should get you going well........ the 1/10th scale 4wd are probably the most popular "Volcano" "Caldera" some of the pro nitro models are popular but the Brushless electrics are taking off.... I would cruze youtube also.