Hope this Helps Some
As Ohiogal said, the exact wording is needed here, for both City Hall and you.
You have a number of questions you are asking, and seem to define a number of terms incorrectly.
I do not know Texas, but I have a useful understanding of West Virginia code in this issue.
1. Advice is often worth what you paid for it. I am just some guy who has walked past a bunch of law books and read bits of a few.
You need to untangle your questions, and straighten out your words.
Simple stuff first - is this for you or he ?
Texas does not have a City Hall - you are likely asking about the laws of a County or City. If so, we need to know that
A Mobile Home is not an RV - The laws for each of these is very different. Is this really a Mobile Home and RV Park ? You speak of selling a RV park, but nothing about selling a Mobile Home Park.
The definition of "recreational vehicle" from the Texas Transportation Code. "a motor vehicle primarily designed as temporary living quarters for recreational camping or travel use. The term includes a travel trailer, camping trailer, truck camper, and motor home." Tex. Transp. Code Ann. § 522.004(b) Supp. 2007.
Note that an RV is defined as "temporary" as well as "recreational" or "travel." This is true everywhere I know, including your own property. Building Codes also define RV and Mobile Home differently. The National Electric Code, in 1 section, views RVs as plugging into an outlet, and Mobile Homes being permanently wired to the electric meter.
It appears that what City Hall is doing is enforcing the "temporary" part of the definition. Also that 90 days is the longest time allowed under the term temporary. This is a common amount time allowed under many laws.
"Moving" in and out is not really a big deal. Put things that might fall in a box on the floor. Raise the stabilizing jacks, unplug the electric, remove the hose for the water, and disconnect any black/grey drain hose and back up the truck.
Take the RV onto a public street, 25 feet is fine, turn around and put it right back in the same place. Drop the jacks, plug in the electric, reconnect the hoses and put the stuff back on the shelves.
Do make sure that the license plates are current, as well as any needed inspections and insurance.
The mixed zoning property would make perfect if the property were used for farming and then the property was divided. The part along the road would have value and was re-zoned as a commercial space, and the back half was left agricultural to keep taxes low.
I can also see it as likely that the agricultural land can be used for 'temporary recreational camping.'
Yes, land can be re-zoned at any point in time. Check with the City Hall Zoning office.
Tags, inspection, and insurance on the RV is all Department of Transportation Stuff.
Ground based water, electric, water and septic is all Building Department / Inspections.
If you are charging rent, you are not just letting people temporarily camp on your agricultural property, you are operating a business. That is a completely different mess.
If you need to make any utility upgrades, they will all have to meet current building codes, commercial codes if needed.
It seems that you are receiving gentle treatment vs what City Hall could be throwing at you. And that you are being grandfathered in any number of ways.
Try City Hall elder services and veterans affairs offices for possible financial breaks, they will not be able to help with Zoning, Building Code, or DOT issues.
Hope this helps