They needed a new roof and the guy quoted my friend over 4x what it should cost. 

It doesn't cost the landlord, all fees are paid by the either the tenant or the prospective tenant.

Just curious, what is a typical cost to de-lead a single family home?  

This could work if there is some equity over the mortgage owed to cover their costs, but not so much you lose out. 

It will save you a couple thousand dollars in financing costs.

A background check is basic and almost no effort and you can certainly pass any cost on to the tenant.

This creates two loan payments ($100,000 of equity and $300,000 on the new mortgage).Key NumbersHome Equity Loan Interest Rate: 6%Mortgage Interest Rate: 7%Rental Income: $3,000 per monthExpenses (management, taxes, insurance, maintenance): $800 per monthIncome and ExpensesMonthly Rental Income: $3,000Monthly Expenses: $800Monthly Mortgage Payment: $2,000ExplanationThe investor earns $3,000 in rent each month.They pay $2,000 on the investment property mortgage and $800 on other expenses.This leaves $200 profit each month or $2,400 per year.However, you have to pay $6,000 interest on the equity borrowed.This leaves you with an annual loss of $3,600.This example shows that while the rental property generates positive monthly income, the interest cost of borrowing the initial $100,000 results in an overall annual loss.

Just make sure you factor in all costs and find out if your heloc allows rate locks and interest only payments.... the goal would be to pay off HELOC ASAP and then use it again to invest in the next property....

You an only you need to know ALL of the costs.  

Taking out the costs for now (lets assume that the finances all make sense, etc.), my question is really around process.