Not too expensive and cover a wide variety of topics.

FHA security instruments require a borrower to establish bona fide occupancy in a home as the borrower’s principal residence within 60 days of signing the security instrument, with continued occupancy for at least one year.Source: https://www.hud.gov/sites/documents/4155-1_4_SECB....

Couldn't you just deduct money from the previous tenants security deposit towards this?

Channel, frequency, firmware, software, security settings, noise in the environment, something as simple as moving furniture around can impact coverage. 

I'm assuming you know the basics of paying in full, on time, etc.Here's a few things that will help fast track to establishing credit -Get an auto loan / a secured loan. 

My term is 1st+last + security. 3 times rent of about 900$ is not something ordinary people (not rich but "working") should have?

I am allocating part of the security deposit for cleaning and trash removal.Looking ahead, I will be much more rigorous about screening the tenants and enforcing my lease. 

I believe you can put down as little as 3.5% and even if you just secure a duplex, you could live rent-free (off the rental from the other side) and could save up faster for your next purchase. 

This would also afford me the security of having around $6K cash flow monthly coming in from my business should I have some unforeseen “bumps in the road” with my rookie real estate investing but also afford me true potential to grow my real estate portfolio.Plan B is to sell my business and use the cash to purchase several multi-unit properties or even an apartment.

I don't understand how people in a very competitive industry can turn down business - especially when I've discussed what I want to do in the next 6 months and told them I have secured my funding.