I use Ally financial for my rental checking and rental reserve account, about the best interest rates you'll find for FDIC insured bank accounts.  

Sometimes a house is distressed to the point where banks won't lend so they can only work with cash buyers, throwing realtors in the mix just slows down progress on finding a qualified buyer.The market I invest in is pretty cool, so a house will sell for 60 or 70k, but it will be on the market for 6 months.  

They still have a mortgage on the property and the bank will try to protect their interest.  

Getting approved for a loan will boil down to one thing: the bank's belief in your ability to faithfully pay back the loan without any issues.

No firsthand experience, but every time I've seen this question come up the responses indicate that for a few small units LLC will not protect you better than simply adding an umbrella policy to your insurance while being more complicated and expensive to maintain.Also many snags to consider such as banks not likely to finance residential property to the name of an LLC, transferring to an LLC later can trigger a due on sale clause in your mortgage, if you mix personal funds and LLC funds to pay for something you can negate all legal protections.

A proof of funds letter would be from someone's bank or IRA account proving they have enough cash in the account to cover the offer price.

You might also have a problem finding banks willing to lend since there usually aren't very many.

@Brian Quigley  Typically if you are not looking for bank financing your progression would be private individuals then hard money.  

(Had to make special arrangements for them to accept a cashiers check with escrow acct info on check and got deposit slip from bank officer after verifying account with escrow company, I almost backed out of deal and it would have affected two other contingencies).I have other questions in regarding the escrow process which I found unprofessional .

The banks are unwilling, or that would have been my first point of thought.