1) Rent and see what you like. Rent a A, B, and C and see what fits your lifestyle the best.
2) Your Audi Q5 is rated for 4,400 lbs towing capacity. Your real limit will be your hitch tongue weight limit (I will assume that as a unit body chassis you will not be able to use a weight distributing hitch) and payload capacity. Research carefully or post up your numbers and people here can help you determine what your max towing really is. There are many, many small trailers you can tow that will give you more flexibility than a class A or C.
3) Cost. Plan on sinking a lot of money into a "new-to-you" used RV. I think the general rule of thumb is $1,000 per model year of age.
4) I think your best route in terms of total financial cost is a used travel trailer towed behind your Audi Q5 if you're only going to use it for a short period.
