As I am accounting for vacancy, capital expenditures and repairs, I have read to use around 5% for each.I am not sure where the 5% comes from.

Ask about the maintenance history.Units: Visit as many individual units as possible to assess their condition and note any necessary repairs or updates.Structural Issues: Be vigilant about signs of water damage, mold, or pests, which could indicate larger problems.Safety Compliance: Verify that the property meets all local safety and building codes, including fire alarms, extinguishers, and emergency exits.Financial and Operational AspectsRent Roll: Request a detailed rent roll to understand current rents, lease terms, and tenant occupancy.Expenses: Get a breakdown of all operating expenses, including utilities, maintenance, insurance, property management fees, and taxes.Income Verification: Ask for historical income statements (preferably 12 months or more) to verify the revenue.Vacancy Rates: Inquire about the historical and current vacancy rates and how they compare to the market average.Tenant Profile: Understand the tenant mix, including residential versus commercial tenants, lease lengths, and tenant turnover rates.Property Management: Find out if the property is currently managed by a professional management company and if you will retain or replace them.Legal and ComplianceZoning Laws: Ensure the property complies with current zoning laws and inquire about any zoning changes that may affect the property.Rent Control: Determine if the property is subject to rent control or other regulations that could impact income.Permits and Licenses: Check that all necessary permits and licenses are up to date.Value-Add PotentialRenovation Opportunities: Identify areas where you could add value through renovations or upgrades.Rent Increases: Assess the potential for increasing rents based on market rates and property improvements.Additional Income: Explore opportunities for additional income streams, such as laundry facilities, parking fees, or storage rentals.Environmental ConsiderationsEnvironmental Hazards: Check for any environmental issues like asbestos, lead paint, or underground storage tanks.Flood Zones: Verify if the property is in a flood zone and the implications for insurance and risk.Questions to Ask the SellerReason for Selling: Understand the seller’s motivation to gauge the urgency and possible negotiation points.Recent Repairs and Improvements: Ask about any recent capital expenditures and future planned repairs.Tenant Relations: Inquire about the relationship with tenants and any ongoing disputes or issues.Due DiligenceProfessional Inspection: Hire a professional inspector to conduct a thorough examination of the property.Appraisal: Obtain an independent appraisal to verify the property’s market value.Legal Review: Have a real estate attorney review all contracts, leases, and legal documents related to the property.By covering these aspects, you’ll be in a stronger position to make an informed decision about your potential investment.

Cashflow is what's left over after you factor in repairs, capital expenditures, vacancy, property management, principal, interest, taxes, insurance.So it sounds like your not running numbers correctly - underestimating CAPEX which leads to over estimating cash flow. 

This money can used by the Landlord to pay their mortgage, set away reserves for structural and roof capital expenditures and most importantly, put money into their pocket.

Mortgage, Taxes, Insurance, HOA: $3040.37Estimated rent: $2475Total Expenses: $3660.12Vacancy (5%): $123.75Repairs (5%): $123.75Capital Expenditures: $100Property Management (11%): $272.25Information when I bought the house in 2022, new constructions Purchase Price: $373000Purchase Closing costs: $4662Current home value: 400k-420kCash Flow: $2475-$3660.12= -$1185.12; -$71107.2 at 5 yearsCash on Cash Return on Investment (CoCROI): 0%Appretiation per year (6%); $535,290.23 at 5 yearsEquity: Loan value $345,089.53 at 5 years; $190,200.47 in equity at 5 yearsLoan Value today 6/2024: $368,201.59Total ROI in 5 years= (Total profit/Total Invested capital)/ Time (in years); Total profit: $190,200.47Total Invested: $71107.2 (neg cash flow) + $42757 (closing sale costs)= $113,864.20Total ROI (5 years)= ROI 67%, annualized ROI 10.8%My biggest concern is that I am relying solely on appreciation and assuming will appreciate at 6% per year. 

.- the current rent will be around: $3700So we will have a difference of $2300 + additional fees like garbage, cap expenditure, rehab loan for the 4 units ( around $350 per month ) and others.

And while that depreciation may be disguised by inflation, or area price increases, money does need to be spend as systems such as HVAC need replacement, roofs need to be replaced, and capital expenditures such as kitchen remodeling are needed for the asset to be rented at a profitable rental rate.

Those numbers would be ok, but do you have money for the downpayment, closing costs, capital expenditures, 15k for reserves?

You may drastically lower your living expenditures and increase your capacity to save for future investments by renting out some of your units while you live in others.Starting with a duplex or triplex is a sensible choice, given your aims and money.

Your capital expenditures should be low, especially if there is a warranty on the work.3.