It sometimes easier to keep your funds under one bank, but in separate accounts.

Well a bank isn't going to lend to a LLC with no history or assets, and since the IRS doesn't consider a LLC a separate entity the bank might not either. 

2) Will I need a separate program for background checks and what should they cost? 

The best way to do it is in a separate bank account LLC or not.  

In the fourplex I lived in, the owner was extra awesome and provided poop bags and a small separate waster container.

If the units aren't separately metered and there isn't a RUBS in place, then you definitely need multiple years of expenses to make an informed decision.There is really a lot to learn about multifamily, and I would say it's more important to build a strong team than it is to learn every detail.

Everything else like bills and monthly payments are in a separate account.

Splitting to separate meters can cost an arm and a leg if you aren’t careful.

I came to conclusion to make thing better, I will be separating utilities meaning get a new boiler and new water heater for each unit so each tenant can be responsible for their own utilities, it will be costly to get a new boiler and new water heater but I think it will pay off in the long runAny advice on separating utilities, what type of boiler and how big should it be for each unit?

To your first question, we do not want investors to guarantee the loan because we wish to separate outthe operational side  of real estate for our investors.