What you are talking about can be had for $5000 or less. My old Astro van can pull my boat or up to around 5000lb travel trailer. I have done it and except for the mileage going way down it did not hurt the van. Blue Book is around $2500 or less.
You can use a porta potti. Thetford makes a nice one for $140.
A RV Air conditioner is around $700, but you will need to cut a hole in the roof and mount it.
A little carpentry can make a bed in a van.
My Astro hitch can support a Generator so you can run the AC and have a small refrigerator both.
My wife and I used the Astro to camp all down the Baja peninsula and it had plenty of capacity for us. I did not add a roof AC because we went down in the winter months, but we could have with some minor mods.
OR as suggested you can buy a used B or C for $10,000 and budget $2-3000 for repairs as needed.
