Short time frame for purchase

[Shawn Merrihew]

I came across a great opportunity. A property with 6 apartments upstairs bringing in a decent amount each month and 4 store fronts on the main floor. Many more details; but my actual question is the current owner is a week away from a tax lien. His objective would be for me to pay the $20,000 in back taxes before the lien gets applied and then do a 3 year owner financed buyout. 

I have one property currently and with this short time frame what are my options for that money? My credits not that great I usually look for properties I can use current cash to buy until I fix my credit score to use loans as other options.