Hello this is about booster's obviously and this would be about the stackability of mobile booster's say if a person bought a paypal booster and they soon decided they wanted to buy a mobile booster, would the mobile booster automatically stack on the paypal booster?.

As far as I've read the only boosters that stack are mobile boosters, so I would guess that the paypal booster + the mobile booster won't stack.

Mobile + mobile = stacks
paypal + paypal = won't stack
Mobile + paypal = won't stack

Sources (Quite old, but still counts I guess...)

http://forum.toribash.com/showthread.php?t=86464
http://forum.toribash.com/showthread.php?t=65927
http://forum.toribash.com/showthread.php?t=64448

so what would happen if i bought a mobile booster now? if i already have a paypal booster active would it just activate next month.

I'm not quite sure myself, but there's two things that I think could happen.

1. It gets activated when the paypal expires.
2. It activates but you only get tc for one of the boosters.

What I would do is wait for the Paypal booster to expire, then stack mobile boosters.