End of the sentence is a bit misleading, because I would expect it to be … at the end?
My trusty Dict of Basic Japanese Grammar says “a conjunction to indicate ‘and’ in an emphatic way”, with rough English meaning “and what’s more; not only ~ but also ~; so”. It’s a more “emotional” form of connecting clauses than with the te-form?
It will never appear as a sentence ender like ーよ or something. But you can omit the end after し to “weaken the sentence and obscure the cause/reason”.
し is also the stem of する, so you need to check which し it is
このアパートはきれいだし、安い。 (This apartment is clean, and what’s more, it’s inexpensive).
遊びたいんだがあしたは試験だし遊べない。 (I would like to play, but there is an exam tomorrow, and I can’t fool around.)