Bent frame or axle from rough use or overloading. Also could be present in any TT that isn't right off the lot.  Ask the seller where he has been camping. If he had taken it on a lot or rough forest service roads it might be better to look elsewhere, rPods aren't well suited to rough road use.

Look at the wheels from behind the trailer. Are the tops of the wheels bent inward (called negative camber)? Uneven tire wear? Park the trailer on a completely flat spot. Does it lean to one side? is the bottom edge of the trailer cabin the same height above ground on both sides (within half an inch or so)? Look at the trailer from the sides. Is the frame straight from the tongue all the way to the rear bumper? 

We spent about 4 mo looking, when we started looking we found 3 yr old 179's from 14K-17K. Prices were higher on the West coast than in the books or on RV Trader. Make sure you watch Forrest River Forum's classified adds as well. It also depended on how often used, number of owners, cabin attachment, condition, etc., as told by owners. Dealers were more proud of their stuff than private citizens. I'd be real careful spending 15K on a 6 yr old rig when newer ones are available, but have not been searching the market for over a year. As often happens, after purchasing at 15K found same for 13K closer to home. :-(   

To get a general idea what you can safely tow, look at the max trailer weight NOT the empty trailer weight. Your actual loaded trailer weight will likely be closer to the max than the empty weight. Then, take your tow vehicle tow rating and subtract 1000 lbs to allow for cargo and people in the TV and a little safely factor so you're not right at your vehicle's limit. Tow ratings assume an empty tow vehicle. If the max trailer weight is less than the tow rating minus 1000 lbs you should be OK. 

You also need to be within your TV tongue weight limit, which is usually listed at 10% of the tow rating. In reality you don't want your trailer tongue weight that low, because low tongue weight can cause trailer sway. Multiply the max trailer weight by 15% and try to keep the TV tongue rating above that if you can..  Once you buy a trailer you can load it with weight in front of the axle to keep the tongue weight in a safe range.

I bought my trailer on Craigslist and had a good experience. I've bought and sold several vehicles on CL. Never buy anything on CL or any other web sales venue without inspecting the item and completing the transaction in person. In my case, money only changed hands at the DMV at the same time as title transfer, because NC requires notarized documents. Also be sure the trailer VIN matches the title. 

Watch out for Craigslist. I got scammed on a Craigslist advertisement. Look at RV Trader. That is more reputable. If you do see something on Craigslist, make sure it is local and make sure you go see it and verify that it is genuine and that the seller has a valid title. Do not send any money until you are 100% sure it is not a scam.

Depending on your Tacoma, you may be able to tow one of the larger RPods. We tow an RP179 with our Frontier. Does your Tacoma have a V6? Is it 2WD or 4WD? Does it have a factory tow package? What is the tow rating? All these are factors in what you can tow.