I assume you mean income tax - I would suggest getting help from a CPA or a good bookkeeper, as you will have other deductions too - like depreciation, interest expenses, etc etc etc   - but for the mortgage, your interest is the expense. not the principal. 

One of my biggest worries is that I'll spend too much time and effort on bookkeeping and organization.

It's not about reservations, bookkeeping and the like. 

I was wondering what the most common/best way to bookkeep for someone that has 10-15 units?

Situation is that I'm about to get going with my real estate investment endeavors, and I'm interested in better understanding how to adequately bookkeep for either one LLC and several properties inside that, or several LLCs (one per property). 

I'll be doing a 1031 for another Multifamily here near Orlando.I've always used paper and pen for my bookkeeping and property management.

@John Fider sole proprietor: one dedicated checking account for all business income and expenses, a saving account/s for Capex (one per property or one for all properties, whatever you prefer), transfer a % of gross revenue from each property into saving/s account regularly, Stessa for book keeping to track the income and expenses for each property.

My gross in August was probably 18-20k I didn’t look that’s my book keepers job.

Just bought my first house hack and I am looking to learn how to book keep and how to do it the cheapest way possible.

Help you with bookkeeping or something.