The rule was changed again in 2018. "Athletic intent" or lack thereof doesn't matter -- you transfer during or after 10th grade, you're losing that postseason.You have to have an address in the district. I don't think you have to pay, though (I could be wrong about that). When Kerry Collins transferred to Wilson in the 1990s, he lived with his aunt and uncle and QB'd Wilson to the 4A state finals. The rules at the time were that he didn't have to sit out for transferring for athletics as long as both principals signed off on it.
The rules changed in 2007 so that you have to sit out a year if the transfer was for "athletic reasons" regardless. When Wyomissing won the state 2A football title in 2012, their QB Corey Unger transferred from Fleetwood when his dad rented an apartment in Wyomissing the previous December. They claimed they moved for academic reasons, but Fleetwood contested that it was for athletic reasons since he held every Fleetwood passing record at the time but the team won 2 games in 3 years while Wyomissing was a state contender that was forced to use an all-county WR at QB after their 2011 starter graduated. The BCIAA ruled in favor of Fleetwood and Unger was forced to sit out until Dec 1 (one year from the move date), which coincided with the 2012 state QF game, so he was only allowed to play for Wyomissing for three games, the state QF, SF, and Final, all of which he won.
This was a very contentious case because Wyomissing at the time was vastly superior to Fleetwood in both academics and athletics, so a transfer for academics wouldn't have looked unusual at all for anyone who wasn't also a record setting QB stuck on a last place team transferring to a state champion caliber program (featuring current Lions LB Alex Anzalone) lacking only a QB.
Only exception is if you can prove a hardship.