Selling Lenovo laptop - Which OS is most likely to sell it?

I have a Lenovo laptop that I want to sell. I'm planning on purchasing either Windows 7 or Windows 8. I'd appreciate your input on my three question below.

Which OS: Windows 7 or 8?
Which version of OS: Home or Professional?
Best place to purchase OS software (license)?
 
Solution
PCPartPicker part list / Price breakdown by merchant

Operating System: Microsoft Windows 8.1 OEM (64-bit) ($88.88 @ NCIX US)
Total: $88.88
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-27 02:31 EDT-0400


At this point, it's likely anybody who purchases a new machine with a qualifying OS is going to want to upgrade to 10 anyhow, so go with the least expensive option, which is listed above. Any professional versions aren't really going to offer anybody other than corporate environment users features that would be necessary or desirable.
PCPartPicker part list / Price breakdown by merchant

Operating System: Microsoft Windows 8.1 OEM (64-bit) ($88.88 @ NCIX US)
Total: $88.88
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-27 02:31 EDT-0400


At this point, it's likely anybody who purchases a new machine with a qualifying OS is going to want to upgrade to 10 anyhow, so go with the least expensive option, which is listed above. Any professional versions aren't really going to offer anybody other than corporate environment users features that would be necessary or desirable.
 
Solution