I would not worry about performance since it won't significantly affect your experience in Gmail, especially since this only gets applied to incoming emails.
I think in this case it is a matter of personal preference. If you really want to have everything wrapped in one filter, then your approach is fine. I would personally recommend separate filters, though, so you could turn on/off individual filters for troubleshooting purposes, or if you change your mind on what labels you'd like to have applied.
For example, if the word "rentals" is too generic and false positives start getting labeled, you'd have to edit that long filter text. If you had a separate filter for each keyword, you could simply edit or delete one filter. Also, if you add a lot more keywords to filter by, it might be easier to just add them as separate filters rather than deal with squeezing more characters into one long filter list.
I don't see any harm in labeling mail from a lot of sources. It all comes down to how precise your filter is and whether the keywords affect only those emails you want and none other. In the end the filters are meant to help you organize your email, and that's exactly what you're using them to do.