So when analyzing, I looked up the long-term rate using Rentometer, BP rent estimator, etc and multiplied by 1.5.

They talk about a multiplier against long term rental  without realizing how many costs should be deducted before you "multiply."

$12,875.00MONTHLY INCOME$9,794.20MONTHLY EXPENSES$3,080.80MONTHLY CASHFLOW13.38%PRO FORMA CAP RATE$83,637.00NOI12 monthsTIME TO REFINANCE56.01%CASH ON CASH ROI25.34%PURCHASE CAP RATEExpensesIncome50% RuleTotal operating expenses:Mortgage expenses:Vacancy:$643.75Repairs:$257.50CapEx:$1,287.50Insurance:$2,200.00Management:$1,287.50P&I:$3,888.95Property Taxes:$179.00Lawn Maintenance:$50.00$330,000PURCHASE PRICEPurchase Closing Costs$66,000.00Estimated Repairs$200,000.00Total Project Cost$596,000.00After Repair Value$625,000.00AcquisitionDown Payment$33,000.00Loan Amount$297,000.00Loan Points/Fees$0.00Loan Interest Rate6.000%Monthly Interest$1,485.00Total Cash Needed At Purchase$299,000.00RefinanceLoan Amount$530,000.00Loan FeesAmortized Over30 yearsLoan Interest Rate8.000%Monthly P&I$3,888.95Total Cash Invested$66,000.00 Financial Info2.16%2% RULE $328,000.00TOTAL INITIAL EQUITY 10.00%TYPICAL CAP RATE 2.14GROSS RENT MULTIPLIER 4.69 / 1.79DEBT COVERAGE RATIO $836,370.00ARV

Then multiply that by the sq footage you are finishing and adding to the home as well.  

What I would do is take the value of the house after you repair it, multiply that by .7 then subtract the 12k.

I have a rental on the market and I want to replace it with something that makes a gross rent multiplier of six or lower and also meets my other requirements.

(est 1,200x.75=900)  So your income would be 1,916.67+900=2,816.67   Multiply your gross income by .39 (2816.67x.39= 1,098.50)1.098.50 would be your likely max payment (this is not exact but it's closeNow subtract your montly taxes and insurance, I would use $125 (insurance) and $250 (taxes)1,098.50-375 (125+250)= 723.50 This is your max principle & interest payment including mortgage insuranceThe rule of thumb is that for every $1,000 you finance your payment is $5/month.  

At the moment, I’m aggressively paying off a little debt using Dave Ramsey’s avalanche approach to ultimately lead me to a debt free start or 0 net worth.

This would mean less forced appreciation, and an assessment value closer to the ARV than when you do a BRRRR on an older house.But to me, this delta based on real estate taxes, multiplied across multiple properties, seems meaningful.

I found a company that will factor my line of credit As cash on hand and will give me a 10x multiplier The interest is 12% and 3 points on whatever I use.