Sporterizing a milsurp rifle made a lot of sense when they were a fraction of the price of the bottom of the line Remington or Winchester, and could be found by the barrel full in the local hardware store. Those days are long gone.
Now you will likely spend $300 in parts to turn a $300 rifle into a $150 rifle.
The possible exception would be the Mosin Nagant 91/30, which can still be had for about $100, (less with an 03 FFL), but with the split top action, and single stack magazine isn't as good a base action for a sporter as a Mauser type.
With a Mosin, you will spend $300 turning a $100 gun into a $70 gun, that probably won't be as accurate as a bottom of the line Wal-Mart bolt gun.
And you will forever be known as Bubba.
Then again, you really need to define what exactly you mean by "build a rifle".
To some that may mean adding a sporter stock and scout scope setup.
To me "Build a rifle" means at minimum squaring and truing the action, installing and cutting the chamber on a quality barrel (Hart, Krieger, etc) turned down to the desired profile, cutting a proper recessed target crown, properly bedded to a quality stock.
Without knowing what exactly you are talking about, it is hard to make a suggestion.
Also, the ability to take down a pump shotgun is really meaningless compared to working on a centerfire rifle. You can take a 500 most of the way apart with a ball point pen. A Bolt action rifle aside from removing the stock and detail stripping the bolt, there isn't much else you can do without special tools. Action wrench, barrel vise, headspace gauges, drill/tap setup (preferably with templates/jigs so the holes go in the right places), a lathe, etc. Even without the lathe (not to mention the skill to use it) the tools alone could easily cost more than the rifle.
What exactly do you want to build?