...i'm looking for a solution to grant access to 1 or several nodes, not taxonomy terms,

so, I got courses and they have lessons, I would like to sell lessons for 1$ and whole course (15 lessons) for 10$,

now i got 10 lessons in my site but in year or so, when i'll have 100+ and then 1000+++ lessons and 10-100 courses - the taxonomy approach will be very uncomfortable