This is over-analyzing. There are no rules of thumb as to percentage of asking price to offer.
Personally, I don't care at all about the asking prices. I offer what makes sense FOR ME, based on either the property's past performance or my own projections. For example, if I know there are 40 of 50 spaces occupied and the space rent is $350, then I offer based on 40 x $350 x 12 = $168,000 annual gross rents, less 35% expenses ($58,800), = an NOI of $100,000. Then I apply a cap rate to that that considers the cost of financing (spread) and the condition of the park. Let's say I can get financing at 80% LTV and 6%, then I'd probably use a cap of 9% for a 3-star park or 10% for a 2-star park. For easy calculations, let's use 10%. Then the value of the park is $1M. Will I offer $1M? Probably not to start. I might offer $900,000, but I'd be willing to pay up to $1M, so I have some negotiating room. If the asking price was $1.2M, I'll still send the offer, but I'll explain why I am offering what I am.
I use the 3-price letter of intent model, i.e., I list a price for each of these options: 1. Seller financing with 0-10% down, 2. Seller financing with 15-25% down, and 3.) 3rd-party financing. Under each, I list the total cash to be paid to the seller (including interest), and an estimate of the tax effects: "Seller may defer payment of one-fifth of the 15% capital gains tax due over 10
years instead of all of it in 2018. 25% depreciation recapture due in 2018. Ordinary income tax on interest paid to Seller by Buyer due quarterly or annually. Figures are estimates; consult CPA for verification."
If anyone wants a copy of my LOI, please email me at firstname.lastname@example.org.