Crazy enough I came across a Delta model 20 variable speed for even less today.
Would you go with the Clausing or the Delta?
-I've run many of the Clausing in shops over the decades, I consider them the standard for professional shops. The Delta, if newer than 1975, seems less robust in construction. However, the condition of any machinery is far more important than the brand. I try not to buy lightweight machinery because I've come to expect industrial duty from anything I buy. I have some consumer grade things and usually have to be more careful with operations. Buying a better built item means better duty and better resale but if it needs repairs you'll need to estimate the cost and whether you want to take on another project or just use the item.
I had a chance to purchase a Hardinge HLV-H lathe for asking price of $2000 (or less) but the bed had been precision ground, meaning the tailstock needed to be raised. This $12000 lathe would have been a great buy but I didn't want another project so I passed.
The Clausing looks a bit rusty and if the spindle bearings are also rusty then you'll need to add more money to it besides the motor. You can feel the bearings by rotating the spindle but it's not the same as hearing/feeling it run under power. Do you want to take a chance with a better built machine or just use it? It would be a tough choice even for me. Good luck, let us know what you decide.