If instead you had 100k worth of available credit and purchased the same 10k worth of goods, that would only be a 10% utilization rate and would barely effect your credit score at all.Some cards offer promo deals such as 18 months of interest free on any new purchases made within the first X months after opening the account. 

Others are just barely scraping by and can't afford more.

And generally, they often times will push you into buying something you maybe cannot afford or 'maybe can just barely if you squint at it the right way' afford. 

I have barely started the estimating rehab costs book and there is a lot of info here.

Some strengths that would mitigate your liquidity would be things like the property debt service ratio is higher than the bare minimum of 1.25 or you are putting more than 25% down on the purchase of the property etc.  

However, because my monthly payments are so high due to the low down payment and PMI payment, a 3 bedroom is usually a negative cashflow or BARELY breaks even monthly. 

. $6k may be barely enough for the furniture, such as beds and couches and tables and chairs, but what about the softer stuff like kitchen utensils and dinnerwares, and bedding and linen, and decorations?

Bookkeepers and Turbo software barely scratch the surface, even for just one unit.Take to a pro and learn to do it right and sleep well when you file.

The duplexes did not throw off nearly enough cash to make up for the difference (not by a mile) and in the end had barely appreciated by the time I sold most in 2014.    

This is not because I am unwilling to purchase but because running my numbers show that I cannot forecast enough return compared to other investment options (taking into account the effort and risk). none of my under writing on RE depicts the return I desire which is the result of rates doubling and prices barely have fallen.