Commercial CNC vs. Homemade CNC Router

I wish to produce parts for a watercraft that I am building. It requires pr=
ecisely dilled holes in thin aluminum sheet metal (.016 – .040) for the purp=
ose of riveting.

I have been monitoring this forum for ideas on building my own CNC router. =
I would require a machine that would accept 4 x 8 feet sheets.

I am looking for your honest, informed opinions. Should I consider constru=
cting my own CNC router or would I be better off outsourcing this work. It s=
trikes me that the construction of such a machine would take some time and m=
oney.

What I wish to do is compare the costs of building a machine and available =
CNC services.

Where can I get work done for me at reasonable prices? What about commercia=
l sign makers? Many advertise CNC systems, would that be a viable low cost =
solution?