I am an RV dealer, but I only sell towables. I have sold motorhomes in the past though. Most any reputable dealer should be able to answer your questions about towing capabilities for a specific MH. If not though, look for the GVWR tag. On that tag will also be a GCWR (gross comined weight rating). Inside you will find a tag usually in a kitchen cabinet, it will also list UVW (unloaded vehicle weight). Use those figures with the following formula:
GCWR ... 17,500 lbs.
Subtract - UVW ... 9500 lbs.
Subtract - Cargo ... 1500 lbs. (remember to take into account any water, gas, etc.)
Balance - in this example 6500 lbs. max towing capacity. These are hypothetical figures.
You should be able to find a good late model MH in your price range. Both the Ford V10 and the Chevy 8.1 are good towing rigs as long as you don't go too long. For best towing results you should probably stay closer to the 25 ft range. I personally wouldn't go over 28 ft.
Hopefully this helps you out.