For example, I've read on another BP thread that if you buy a $100k property and use only $20k as a down-payment, and $80k in debt from either a private lender or bank, that you would then be required to invest only $20k to improve the property (not a full $100k as others have suggested).Those are just basic number to get the gist across. 

Also, you generally cant leverage since banks won't allow you to fly uninsured!

I am looking for lendors or local banks in Houston, TX that will do portfolio type loans for a cash out refinance or no cash out refi without the 6 month seasoning period.

Doing some local bank hunting can save you lots of money.

What does the bank look for in order to get a second loan.

Typically an investment property financed with a bank requires 20-25% down.

My question is referring to conventional banks.

I personally chose to max my 10 loans with conventional banks at better rates before doing commercial type loans.

You can start one up with a local credit union or the bank that you currently use to hold your money.

i would always choose multiple, and tell them all upfront your one of three upfront and first Bank to fund at the rate I expect gets my business. competition always motivates people.