from $0 to $100 or up per month !!! for many types of link
There are many free services for
exchange links, add url, submit url.
Why not try free things first.... so you many get some basic ideas about the "link marketing"
and
then you will be more easy to decide ::
where to add link or submit,
how to maintain or to check,
what keywords to use,
when is the best time,
how much to spend.......