$25/ft and $5k/each major (roof, plumbing, elec, foundation, HVAC) is a ballpark that works but you have to adjust up or down for ARV and finish and whether you GC or hire a GC.

I would say your best bet is just sitting down and seeing if they know their stuff.

I've read stories of mixed success with laundry vendors here on BP, but I guess it could be a safer bet with local companies.Would you manage your shared laundries in house given the option?

I think the sites and their estimates are pretty impressive considering they contain virtually every home in America, often with interior pics, but they are what they are: free tools that used automated formulas to predict something that can often be a bit unpredictable and can't fully account for the human emotional factor (for example I bet something like the Brady Bunch house zestimated far less than than its actual value)

I bet it's less than you could get somewhere else and you're building equity, learning REI, and taking positive action.

In a case like this, if there is a mortgage, bet your firstborn the lender will bid to get the tax lien (potentially up to the market value or the mortgage amount) to secure first lien position.

We currently have a local bank that is willing to make the loan but it will be on an adjustable rate.  

20 year adjustable mortgage?

Your best bet is to try to find someone to work with/for in real estate to learn the ropes and make some money, put in a lot of hours and hustle, connect with as many investors as you can through local meet ups, and just keep grinding until you start seeing results. 

From what I've been learning, your best bet for a park of that size is to find an onsite manager.