I am not a member of Phi Alpha Delta
... but am familiar with their site etc and have met members of the org. I'd advise looking on their HQ website www.pad.org
as it has lots of great info.
In reference to your questions...
The pre-law initiation fee is currently $70
This will also entitle you to a discount of $10 on the law school chapter initiation fee upon later joining that. The discount figure may or may not be varied.
There are not further national dues for pre-law chapters in the same way that some fraternities will charge semesterly or yearly dues. However, P.A.D. does have a Capital Campaign fund, proceeds of which go toward paying off financial commitments (mortgage etc) so that in the future more money can be invested towards members, programming etc. Many chapters donate to this.
In terms of chapter
dues, some chapters do charge (semesterly) small amounts to members to enable the group to actually put on events, activities etc. This varies from chapter to chapter, anything from $10-50; the average being $20-30. Some are as low as $25-30 per year. However, not all chapters charge this and most that do likely have payment plans and other such arrangements. It's by far best to actually check with the individual chapter you become interested in regarding that.
I hope that helps.