What I could see making MF worthwhile is value add, where you increase total rents by a significant percent (due to improvements you make), thereby greatly increasing the value of the property.

Pay down debt, budget/cut expenses, increase income, and finally save/invest.

.$2,135.00MONTHLY INCOME$1,694.08MONTHLY EXPENSES$440.92MONTHLY CASHFLOW14.08%PRO FORMA CAP$9,853.40NOI$22,125.00TOTAL CASH NEEDED23.91%CASH ON CASH ROI13.59%PURCHASE CAP RATEExpensesIncome50% RuleTotal operating expenses:Mortgage expenses:Vacancy:$170.80Repairs:$213.50CapEx:$106.75Electricity:$50.00Water & Sewer:$162.00Insurance:$120.00Management:$213.50P&I:$380.20Property Taxes:$277.33$72,500PURCHASE PRICEPurchase Closing Costs$2,000.00Estimated Repairs$2,000.00Total Project Cost$76,500.00After Repair Value$70,000.00 Down Payment$18,125.00Loan Amount$54,375.00Loan Points$0.00Amortized Over30 yearsLoan Interest Rate7.500%Monthly P&I$380.20Total Cash Needed$22,125.00 Financial Info2.79%2% RULE $15,625.00TOTAL INITIAL EQUITY2.83GROSS RENT MULTIPLIER 2.16DEBT COVERAGE RATIOAnalysis Over Time3% /yearEXPENSE INCREASE 3% /yearINCOME INCREASE 2% /yearPROPERTY VALUE INCREASEYear 1Year 2Year 5Year 10Year 15Year 20Year 30Total Annual Income$25,620.00$26,388.60$28,835.54$33,428.29$38,752.55$44,924.83$60,375.21Total Annual ExpensesOperating ExpensesMortgage Payment$20,328.97$15,766.60$4,562.37$20,801.97$16,239.60$4,562.37$22,307.82$17,745.45$4,562.37$25,134.21$20,571.84$4,562.37$28,410.77$23,848.40$4,562.37$32,209.20$27,646.83$4,562.37$41,717.40$37,155.03$4,562.37Total Annual Cashflow$5,291.03$5,586.63$6,527.71$8,294.08$10,341.78$12,715.62$18,657.81Cash on Cash ROI23.91%25.25%29.50%37.49%46.74%57.47%84.33%Property Value$71,400.00$72,828.00$77,285.66$85,329.61$94,210.78$104,016.32$126,795.31Equity$17,526.25$19,494.41$25,837.43$38,134.84$53,197.53$71,986.64$126,795.31Loan Balance$53,873.75$53,333.59$51,448.23$47,194.77$41,013.25$32,029.67$0.00Total Profit if Sold *-$1,449.73$6,062.22$30,895.02$80,784.39$143,073.13$220,258.21$432,774.81Annualized Total Return-6.55%12.87%19.10%16.62%14.34%12.71%10.60%

If not, you may need to increase the septic to handle two family, per your county health dept codes.

However this can result in extra fees hence increasing money to the City.  

@John Woodrich"Equity doesn't kill cash flow, equity increases cash flow."

Your expenses after taxes remain the same as well so you can save $160 per month (until your real estate property taxes and insurance increase). 

Does it make sense to increase my home debt to invest in other property???

Knowing that, if I did buy the property, I may slightly increase rents at renewal time.

. $100k under the county appraisal is not to low - just work with your numbers. you can put it on paper with 30 working days Due Diligence clause and option to increase it by another 21 days.