Will it cost less?

Will it cost less if I do part of the patent effort myself?

No, it may not cost less. On the contrary, it may cost more in total, as the patent agent still has to go over the entire patent effort, and more often than not, has to correct errors on top of it. Moreover, some errors cannot be corrected, as there are strict provisions in patent law, and you could lose part or all of your patent protection.

Engage your patent agent from the very beginning of your patent effort!