In 2011 I created a bike trailer from a golf cart and you can review the steps I did to convert it to the trailer in my first instructable. I have had it in use since then and I have another thrift store bike and improvements to share. Thanks to dbc 1218 bicycle cargo trailer instructable for the hitch idea and source.
The original universal and hitch design failed after a couple hundred miles. I created another and then I saw dbc 1218 instructable and adapted his hitch to my trailer. I moved the bike hitch frame down and adapted to attach to the existing threaded mounting holes near the rear axle. I found the appropriate size bolts at the local chain hardware in the metric bolt selection. I found after a few weeks I needed to use loctite as they loosened up.
I had to replace the wheels of the original design because of an accident and bought another $7 golf cart from the thrift store. It had a folding handle that I adapted to work as a stand and adapted a web strap from same to strap it up when in use.
I would like to have a different basket and haven't found what I would like to be permanent, therefore I am using bungees to hold it on the trailer. Just a personal quirk at this time. I am thinking of small bike tires for the trailer too if I can get them free.