If you decided to use a average of the maintenance cost for the small car and the wrecked Humvee, you would be wrong on both.Even if such a universal maintenance constant could be determined, multiplying this constant (percentage) by the rent does not work.

I was just asked a question via PM that I thought I should post here on this thread as it is very applicable to the topic.The question was, if the renovation costs should be estimated by taking $15 per square foot and multiplying by the number of square feet of the property.Here is my answer:"You are doing it wrong as you were advised incorrectly.

To calculate the B/S/H, you take the $140,000 ARV, and multiplied it by 15% which equals $21,000 [$140,000 x .15 = $21,000].You decided that your profit should be $10,000 as the Assignment Fee for a wholesale.The Investor Buyer’s profit is calculated by multiplying the Rehab costs by $1.25 to get $19,000 [$15,000 x $1.25 = $18,750].Now, plug all these figures into the MAO formula and you calculate that the most you can offer on this property is $75,000.

For example, let's say my pro forma uses the following assumptions, excluding any vacancy:Monthly Rent: $2,000Monthly Expenses, excluding mortgage: (Taxes, Insurance, HOA, CapEx, etc): $1,750NOI: $1,550Mortgage Payment: $1,300Monthly Cash flow: $250Now if we assume a 5% Vacancy Rate = $100 and include it as a negative revenue, NOI Margin (NOI / Income): 76.3%Cashflow Margin (Cashflow / Income): 7.9%Gross Rent Multiplier (Property Value / Annual Rent): 7.242% rule-of-thumb (Income / Purchase Price): 1.15%50% rule-of-thumb (Total Expenses / Income): 23.7%If we instead assume the vacancy rate is an expense: NOI Margin (NOI / Income): 72.5% Cashflow Margin (Cashflow / Income): 7.5%Gross Rent Multiplier (Property Value / Annual Rent): 6.882% rule-of-thumb (Income / Purchase Price): 1.21%50% rule-of-thumb (Total Expenses / Income): 27.5%I realize it may not seem like a material difference in this example, but I imagine in some scenarios it  could lead you to make different decisions just based on how it's classified.

So, even though you have a large downpayment saved up, you won't be able to multiply it by 4 to figure out how much property you can buy.  

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.

Figure out how much you make running your business per month, multiply it by number of months remaining, and start there.

Rental rates, gross rent multipliers, cap rates, demographics, etc)?

The overall average price per sqft came out to be $138.25 and multiplied to the homes sqft I came to a price of $198,000.

Multiply that figure by a factor of ten.