If you have 1 and 2 bed units, you would typically divide bill by number of bedrooms, and multiply back the number in each unit.As for snow, personally, I always had tenants take care of any individual use areas, i.e. a small porch that directly access to only one unit, the tenant needs to shovel and salt that area.  

On a $450,000 house even if he clears  your optimistic $2,500 a month your talking about a gross rent multiplier of less then half a percent per month.  

Then take that taxable income of $3,701 and multiply that by your appropriate tax bracket %?

To be confident moving forward, I would check Rent comps for my terminal product's units, draw that up into GOI, calculate expenses or just multiply by 0.7-0.75 to subtract annual expenses (utilities, maintenance, taxes, insurance, etc) and arrive at NOI, then subtract my other expenses (like debt/loan payments) over the year, to see what we're looking at in potential CF once fully stabilized.

You take he non-passive losses you have multiplied by your marginal tax rate.  

These estimates always tend to show the max amount of bonus deprecation multiplied by the HIGHEST tax rate = your estimated tax benefit.  1) Most of us are not in the highest tax rates and:2) Tax rates step both up and down, so you can't simply take the bonus depreciation multiplied by a tax rate. 

Exactly, a BIG multiplier.

I’d have to know more about location, most of the shore (and this isn’t a hard rule) but if you take you pp and multiply that by 0.075 than divide that by 12 is a good starting point.

If you want to be conservative on your estimate, you can take the total purchase price of the property and multiply it by 40% then apply the millage rate.

Equity Multiple:How many times you are multiplying your money when it's all said and done.4.