What type of RV do you have?......Duh! I just read you have a hybred.
Storing inside a farm building presents a variety of problems. I am a farm girl. I have seen damage done to RV's stored in driving sheds.
Mice/ squirrels being the obvious....plug all holes (water tank drain) with steel wool, silicone or spray foam (be careful) Some people swear by using moth balls inside others fabric softener sheets. I have tried both things storing a tent trailer. Mice/squirrels will/can chew through canvass, make nests in mattresses. ( I would remove them). Also, don't rely on plastic containers.
Birds....your trailer is guaranteed to be covered with bird poop unless you cover it.
Raccoons....I have seen damage from a raccoon going underneath and chewing/tearing through. One man puts barbed wire around the bottom of his to keep them out
Spiders..,You could get spiders anywhere really but they like to plug gas/propane lines.
Smell....even in an out building your unit will pick up the odor. What type of farm is it? Cash crop or livestock? You will get a lingering odor.
Insurance....make sure you have ins and let them know where your trailer is being stored.
I really would like to discourage you from storing on a farm. From experience it can be one of the worst places to store your RV. This coming from a farm girl LOL. Talk to one of the local vets, they may be able to suggest something to keep critters away.