If money is an issue, I would just buy a model 7 in 260. I see them on gunbroker all the time and even if they are priced in the $600 + dollar range it will most likely be more cost effective than semi-custom rifle
If you were to go ahead with building a rifle in 260, then you would have to find a donor rifle for the action, have it trued (if you are going to the expense of a new custom barrel) then get a custom barrel and custom stock, etc.
I would look at some other manufactures besides Remington for the build. Would cost you same if not less money (Stiller Preditor or Kelby Atlas) and have a very high quality action as a resut. Both are around $700, which is less than a donor rifle and cost of quality smith work to true it.
I have had great success with Krieger barrels, but there are several other excellent barrelmakers. Costs about $325 and up for blank. You will have to have someone chamber, headspace and fit it for you. The cost of that depends on the smith.
Then you have a custom stock. Hopefully one that has a full length bedding block. Otherwise, you will need to have someone pillar and glass bed the action.
The list goes on and on...
But the point of the story is that when you get into the custom rifle
game, it is expensive. There are those who would put $2000 set of tires/rims on a $500 car, but you still have a $500 dollar car.