Depends on the bank and the buyer. If you are a new buyer and never owned a park, then the broker is probably trying to qualify you as best as possible. Keep in mind that you may be competing with cash buyers who have bought multiple parks in the past. Also, this is not like buying a residential house where you can get a pre approval. Commercial loans are underwritten on the value of the property, not the buyer. Banks generally do not provide pre approval letters on commercial deals. If you can swing it, provide some other proof of funds.
The LOI before seeing financials is backwards, but since it is not binding, you could comply. Once you see the financials you may have to adjust your price or retract your offer.