I have investors that I set up loans with private money that only use this method because of the speed.

You can also use the Enemy Method to check the rates of your competitors.

You can also check online resources like BiggerPockets or Roofstock, which offer general CapEx guidelines based on property type and age.These methods should help you perform a solid preliminary analysis.

Payment methods, tax collection etc.

There is no 'per square foot' method that is accurate....At least until you have quite done a few.... 

Something to consider is to convert the pre-tax funds/assets to Roth so you have tax free atm withdrawals at retirement.  

@Elizabeth RossFor properties under 100k you will likely need to use the BRRR method as its difficult to get a 30Y loan on a properties valued under 100k.

Or should I consider withdrawing smaller amounts, like $100k?

I need a suggestion here to handle maintenance and cleaningTURNO for automated cleaner payment and scheduling along with inventory trackingQuickbooks / Bookkeeper to keep my PM business in alignmentChase bank & trust accountI'd like a better method for managing linens (bulk order) and distribution.I'd love to compare property management / cohosting agreements with someone to share best practices. 

The straightforward method is to do everything yourself, as in my example above.