This is because I do not like variable rates (HELOC) for long term.  

@Angelina Callaway Determining whether to do a cost segregation study or not has a lot variables.

I think there are always other variables that come into play when discussing cash flow. 

I would consider looking into ADUs (additional dwelling units), can do garage conversion for 50k or so (depending on variety of variables), and rent out with good ROI.

Every column need to be a variable( quantitative variable and also Categorical variable).I want to do my task on real estate( any kind), so I need to found a spreadsheet that answers those I writing above.If someone can help me with that it would be amazing!

The furnace was new and very efficient outside the variable speed motar.

My HELOC is a variable rate so I do run the risk of them increasing the interest on it. 

Weekly vacation rentals have variable prices, so early in the summer is cheaper, July and August are the most expensive, and September might rent out for a few weeks. 

Lots of variables on the costs and time first off by unit and circumstances...For example, there any major items you need done like a hot water heater, new flooring, or appliances.

If you dig in, the answer is that they looked at different variables.