At the moment? Large enough that it realistically can't be done. Millions and millions. Millions of tons of equipment, too.
Emerging technologies (nanotech...) may be able to reduce this, but for the moment it's perfectly realistic to consider scenarios where new colonies usually regress to 18th/19th century technology for a few generations. This, of course, makes colonizing uninhabitable planets such as Mars... hard.
Mars we could probably do, it'd just be costly. An interstellar variant? Not likely.
Emerging technologies (nanotech...) may be able to reduce this, but for the moment it's perfectly realistic to consider scenarios where new colonies usually regress to 18th/19th century technology for a few generations. This, of course, makes colonizing uninhabitable planets such as Mars... hard.
Mars we could probably do, it'd just be costly. An interstellar variant? Not likely.