Do I just take the price per square foot, multiply that by a decent sized bedroom and subtract that from the sold price for the ARV Comp?

I don't know what the seasonality for that market is but if you can figure out the average nightly rate for the year then you multiply that number by the amount of weekend days you estimate will be booked.

That will give you a multiplier once you understand what the NOI of the operation is and what you are actually selling as a revenue stream.  

Multiply that by the cost/month in 4 for each line item, sum them up, round up or add margin, and you now have how much you need currently in cash in your capital reserve account.

(they use Gross Rent Multiplier on their appraisal form, but same difference) 

Normally it's a multiplier of the revenue the business does annually.

If you use hourly labor (Like I do) personal experience helps a lot- take a look at each project and count the days and multiply by your guy’s daily rate, then do a rough estimate for materials.

Full disclosure, I sell the All In One Loan and i personally use it to multiply real estate. 

There’s nothing to multiply your investment in a flip in these areas — especially at the bottom of the barrel. 

When you buy a list guess who else has that, EVERYONE, so congratulations you get to be 1 of 1,400 of the exact same annoying junk mail in someone's mailbox, and your open and action rate drops by a BIG multiplier.