They can use a cell phone and sort of use a computer, but that's about it. 

Which ever you choose don't speculate or base an investment strategy on an unsustainable appreciation trend.

I charge two months rent or remainder of rent to fulfill the contract, whichever is less.

Use Experian Boost from the Experian credit report site to use things like your cell phone bill being paid on time each month to improve your credit and your rent being paid on time.

but is there any chance to find skip tracing services that give me only 1 best phone number to each owner and with high accuracy.No, people change numbers, especially in this day of cell phones.

So the agents these days are Taught to put this one their cell phone  " Thank you for calling for faster service please text me "  well that ends it for me :)  the few times i try to engage in a text conversation I just get way to frustrated its too slow. theres no personal inflection I want to talk to agents to feel out If I think there is a light bulb on or if they are suitable for my needs I can do that quite quickly on the phone.So to answer the OP  I am not sure what you do to get anyones attention these days in the go go text dont talk modern world. 

This is so I can have proof that whichever lawyer I choose to hire has successfully completed a real estate transaction for a buyer in Oakland California.Thanks!

Hopefully within the first couple off hours of it going up for sale    I don’t go see it  I Google the agents cell phone number I send a text with a picture of my drivers license screenshot of my bank account list of properties I own in the area from the county website and put my offer inFor me this is what gets me fixer uppers in this market 

Cell phone pictures are not good enough. 

If you qualified with your credit file, the loan would be based on the fair market value of rents or existing leases, whichever is lowest.