Pay to play
In the personal ads that I have seen, LOS means Lost or Stolen.
Androgynous
For sex :)
Long Term RelationshipLTR in personal ads means long term relationship.
OHAC mean in Relationship
friends with benefits.
Bareback, or no condom
water sports
In Search Of
professional
"short Message service" in other words text. It's not exclusive to personal ads.
PNP in personal ads means party and play.