Used houses in the area sell anywhere from $75-125 a square foot.These are long term rentals that I do not plan to sell.I am reading the Rental Property Investing book and implementing the method that focuses on cash flow and that strategy states you need to have $300 cash flow per month, per property.

You have numerous funding options so pick your poison.

These methods include: Detailed Engineering Cost ApproachDetailed Engineering Cost Estimate ApproachSurvey or Letter ApproachResidual Estimation ApproachSampling or Modeling ApproachExperience or “Rule of Thumb” ApproachIt’s important to understand the differences between the approaches including which one best fits your property and the reliability of each approach.DETAILED ENGINEERING COST APPROACHThis approach compiles the costs from construction and accounting reports to build a report.

There are also people who swear by one method or another.   

I have gone to numerous RE meetups and discussed numerous ADU appraisals and was heavily involved analyzing one (that gave a value of ~$50k for a ~400’ garage conversion 1/1.  

Hey everyone, what tools/method do you use for estimating the cost of maintenance and repairs of a multi-family home (2-4 units) ?

Search the BP for ADU appraisals to encounter numerous examples.

Find Brandon's videos on YouTube for the "four square" method of analyzing homes and practice.

I can find numerous other similar homes for investors.

Probably going to be a check.Smart contractors are starting to understand that convenience matters to customers and being able to take different methods of payment can help them collect their money.