This could be a flat fee or a percentage of their assignment fee.

Percentage down. 

Our property has cash flow and according to the many bigger pockets podcasts I’ve listened to you shouldn’t just pocket all cash flow but set aside a percentage to cover reserves, CAPEX, vacancies etc.

My longest recent rehab was 2.25 months and added a half bathroom, took down 4 walks including load bearing, put up 3 walls, new plumbing, electrical, flooring, huge percentage of drywall, an eye brow porch, new kitchen with full layout change and new bathroom with full layout change.  

Its not a set price per unit or building but rather a percentage of income to debt.

Your insurance is going to be highly variable and I wouldn't use what an agent or the seller tells you as the cost of dwelling policies have increased substantially over the past few years due to rising new construction costs. 

To me it seems your maintenance percentage is a bit low.

There are many variables that increase real estate returns and they are rarely addressed when comparing it to the stock market.

However, understanding their requirements—such as down payment percentages, reserve requirements, and loan-to-value ratios—is key to getting approved.One of the biggest advantages of working with portfolio lenders is their ability to fund deals that traditional banks might pass on.

There are just numerous variables and calculations you must analyze to check.