Does paper acceptance mean an on-site talk is required?
Personally, I have only seen conferences which require every paper to be presented on-site. Most conferences explicitely state that paper will not be published in the online proceedings, if the authors do not present their paper. If this is not stated on the conference's website, please write to the committee.

However, I recommend you to find a different solution. Discussing a paper at a conference is a very important part of your scientific career since you get in contact with other researchers. If you encounter financial difficulties, you can write to the committee and ask politely for a waiver or reduction of the fee.