Walk-ons are not the end of the world. Unlike in GD, where you are stuck with the player for 4 years, walk-ons do not automatically get a scholarship. They are on your roster for 1 year, and when that year is over they leave. Giving you another 'ship AND monies to recruit for it. So taking a walk-on or two is a great way to balance out classes and have some extra money available. Also, Its adviced to take a walk-on over a scrubby player who will sit on your bench for 4 years.
Note: Taking more then 2 walk-ons gives your team a pracitce penalty, your players won't improve as fast as normal. So try to keep it at 2 walk-ons at the most! Or if you get in a bind, give your best walk-on a 'ship or just deal with the Penalty. (With the introduction of FSS, the practice penalty is almost non-existent).
D1 Recruiting Tip: During recruiting I find it very worth while when starting to build up a new program to recruit expecting to take one or two walk-ons. The added 15-30k that you will have to use towards other recruits to begin your rebuild can be very helpful.