Parking them is good if its a valuable keyword in there, like debt or something.
Typo generators are good but your best typing shit in notepad yourself about 100 times trying to type in that domain. Then count which one you typed in wrong first, and buy it.
Typo generators just generate randomly, you doing it yourself you know will work

It honestly does depend on the niche of the site whether it would be worth it to park, you say its free to park, it is yes, but you could (if its a good niche) send it to some affiliate link using the free URL redirection domain registrars give, and using a seperate subid in the affiliate program to track the hits.