You are talking about a full bore frame-off restoration. The materials are going to run a couple of grand. Then of course, you will probably need axles and brakes all around, new tires as well. Appliances are probably dead or near dead... Then there is the problem of the hundreds of hours of your time. If you ever finish (and many give up when the true extent of the job becomes apparent) you will own a relatively pristine example of an old trailer. Realistically, when you go to sell it, you will find out that your time earned you much less than minimum wage.
Now, if you are looking to do it as something fun and hope to end up with a trailer that you will own until you die, well, why not? Keep you off the streets and out of the bars...
If you actually want to go camping in the near future, keep looking.
Just my 2 cents...
Old (usually dirty) Nissan Titan
Old (enhanced with "male pattern baldness") Sovereign
Young, lovely bride
Goofy dog, dismissive cat