Currently my wife and I are debt free including credit cards and saved up a decent chuck of change for retirement, mutual funds, stocks, and too much into CDs(lucky only one year at 3%).

So many "cash" buyers have commercial lines of credit, Home Equity Lines of Credit (HELOC), even credit cards with significant lines that allow them to convert money into cash quickly. 

Automated post cards via click2mail or yellowletters maybe 2% response using the same list.  

I have 2 credit cards and a auto loan.

THIS would also be a great time for you to go apply for some 0% financing credit cards (which I also did). 

#NRAinstructor Feel free to ask me how to get your CCW card for Arizona.

I think it is better to start small than to over leverage from the start and build a house of cards that one overlooked expense can cause to tumble.  

Other options might include: getting an unsecured personal loan to cover the $20k, persuading a friend or family member to loan me the money, or cobbling together the money from random sources like credit card convenience checks and maybe a Lending Club loan.Problem is, while my credit is good and I have a decent amount of cash to work with, my income is low-ish and comes from four (!)

@Tony Gunter  agreed you NEED the no state income tax to offset the property tax's.. for those that live in high state income tax's like were I do Oregon or CA.. buying and holding in Texas can be pretty costly thing to do compared to other buy and hold markets... you really NEED that appreciation card to make sense of buy and hold in Texas in my personal opinion.

If that does not work, a Hard Money Lender (HML) or credit cards would be another option.