[The Bald Man]

I want to build an under-ground lair, starting with a bolt-hole and upgrading as I go.  I plan on doing the work myself, so my only cost is materials.  I see this a 'related' to purchasing a permanent lifestyle, but not identical as it doesn't include the consumable portions of lifestyle (clothes, food, etc.).  Permanently buying a lifestyle is 100x the monthly cost. 

Anyone out there have recommendations? 

[Blue Rose]

This is not a permanent lifestyle.

This is a building.

Anyways, it's an extended test of some arbitrarily defined interval and difficulty.  You could research what's involved in similar projects in the real world for an idea of price and time frame.

[RowanTheFox]

I agree with Blue Rose.

IRL, the smallest, most basic underground bunker will cost you approximately $6,000 USD, and that price can vary by brand or what materials you use. That's JUST for the bunker. That doesn't include the cost of digging a hole to put it in. A really GOOD bunker can cost upwards of $60,000 USD, and that, again, is just for the bunker.

The type of soil you're digging in will also affect the price. Digging into soft sand or loam will be cheaper than trying to dig through hard clay or rocky soil (meaning your tools will break more quickly and have to be replaced). If you're a magician with a Shape Earth spell, you can probably ignore this part.

[Reaver]

Other things to consider:
Heating/cooling
Water
Air
Waste disposal (liquid, solids, gases)
And then we get to ammenities!
Electicity
Cooking
Laundry
Refrigeration


Average price for a home (construction cost) is roughly $76 to $175 a square foot. (The range is so vast due to different materials and finishes. Bare concrete is not actually that cheap @ $90/sqft)

[MijRai]

While it is a building, the construction could be used as a way to justify making it into a Lifestyle; rolls to surreptitiously hook it up to the power grid without getting caught, hooking up to water mains or somehow drilling your own well, etc...

As a GM, I'd probably end up charging 75% of what a permanent Lifestyle would cost if you do all of the work yourself to make it a 'permanent' Lifestyle.  This doesn't factor in time or other variables.