For an open trailer to tow a motorcycle, the Ken-Don trailers are awesome. Not terribly cheap new, but if you cruise craigslist (and just search for "motorcycle trailer" and click everything to look at it to see since people sell this without even knowing what they have) you can find one for under $500.
That's what I did. I think mine was $400, but it did need a decent amount of TLC to make it look nice again (and a little welding to get the third leg working right again). But they fold up really nice for storage in your garage, which keeps you from needing to replace tires due to dry rot nearly as often. They tow and ride great thanks to the torsion bar axles.
There are single and dual bike models and I'd only buy the dual, personally, for resale and flexibility. The dual will haul a single bike just fine. I modified mine by adding an easy to remove 2" receiver hitch to I could put a 2 bicycle bike rack on it sideways and still haul one motorcycle, and it works great.
For Rodney, it's real shame nobody makes something like the U-haul "sport trailer" to sell. Those are popular with the One Lap crowd as they hold a LOT of stuff but are very low profile and aero and light. Don't know if you could get TWO full sets of tires in one, but it would be close. They hold more stuff than you'd think from the pics of them. But U-haul doesn't sell used trailers ever, and the manufacturer of those did an exclusive deal for U-haul, so they don't exist outside of being rented.

--Donnie