You can purchase LR 5 from Adobe as a Perpetual License not the "monthly paid Creative Cloud version".
To purchase LR 4 you will have to search for a third party reseller like Amazon, eBay, Best Buy etc.
LR 4 is not available for sale from Adobe. LR4 is the last version that will run on OSX 10.6.8+, Windows XP and Windows Vista. You may be able to find it still for sale on Amazon, but be careful of scammers that aren’t Adobe authorized resellers and are probably selling pirated software that won’t be able to be licensed. Also don’t buy the $80 upgrade version when you’ll need the $120 full version. The upgrade and full versions function the same, but the upgrade version requires having a previous version’s serial number in addition to the current version’s serial number to be licensed. Since you’re just starting out with LR you wouldn’t have a previous version serial number.
LR 5 is available for purchase both with and without paying a subscription. LR 5 requires OSX 10.7+ or Windows 7+.
If you are interested in LR 5.x without paying a subscription then download the LR 5.6 update from here, and run it in trial mode for up to 30 days, to see if it’ll work on your computer and with your workflow:
For completeness, here is Subscription LR5 which includes PS-CC for $10/month (U.S.):
The subscription version is the only one that has LR Mobile sync capabilities.