I am doing a wedding cake for my nephew and niece-to-be and I gave them some ideas that I thought I could pull off and the one they picked a square with 4 layers.  12,10,8 & 6 inches

What I didn't take into consideration is how expensive the cake pans are and how I should have purchased them over the last couple of months instead of waiting until the last minute.

I purchased a 12" x 3" fat daddio pan for $25 and I have a square 8" pan already.   

Is there any chance that I could bake a 12" and cut it down to be a 10"?  

Could I cut off the edges or would it be better to cut it down the center both ways and take out the amount of cake to make it 10" and sandwich the pieces back together with icing?  

Or should stretch my budget and buy a 10" and try to turn an 8 into a 6 since the 6 wont be supporting anything.  

Buying the 12, 10 and the 6 would be too much since I am doing this for free, I would be spending nearly $60 on just pans for a one time thing.

I dont know anyone who has pans I could borrow. 

Cakers carve cakes all the time.  So to answer your questions Yes.  Carve the 12 inch down to a 10" by cutting a half inch all the way around. etc.

When your budget warrants buy the pans you will use the most first.  Common sizes.

AI would do it that way, if I had to. I would just carve 1" off all the way around. You could make the 6" in the same pan, just section off half of it with foil, and use dry beans on one side, batter on the other, and chop it in half. When I had to do that, I made it a little wider than needed, in case I had to trim.

Hi, I'm not sure where you are based, but many of the cake shops round here hire out all sorts of tins.  I recently hired a 12" round for only £1 (plus a £10 refundable deposit) so it might well be worth your while investigating that if it's not too late.
 

You could also check out local cake supply stores, mine rents pans for a couple dollars.

Yes, Annabakescakes and CWR41.  Don't know where my head was at the time.  Your both right.  Its 1 inch on each side to cut down to a 10 inch cake.