I know its American & some items will be different, but its gotta be fairly similar.Are you using the BP rental calculator or something different?

I have used this attorney for a few years for several small simple items including drafting the leases that I curently use. 

Also once we started working on the duplexes - we introduced ourselves to the current tenants in the other half of each duplex, and asked if there were any pending maintenance items.

Welcome to BP @Javier Sanchez You have come to the right place to get as much knowledge and actionable items to get yourself going.

A cage sometimes will help, maybe a camera would help capturing whomever is doing this

If you are true partners and upon success, intend to repeat this, you should form an entity together with an operating agreement that spells out each and every soecific item (responsibilities, tasks, money, what happens in case if death, etc. as far as thevowner carried financing, have your attorney draft up a note and deed of trust.

@Muz Khan lots of items in your post so I will try to handle them one at a time here:If you find a HML that doesn't lend to first timers then keep shopping.  

I would show him an itemized list of exactly what my offer is what it is and let him try to argue with it.My $0.02 ...

What items are in your Monthly Operating Expense total? 

Many of our items are brand new, so you can't compare old things to new things.