I'm currently building up a bike from a bare frame using parts from a different bike. But the frame is used (but looks brand new), and had previously had a headset and BB installed in it. My existing BB and a new headset went right in without issues. I made a homemade tool to press the BB cups in, and I already have tools like a Shimano square taper BB tool on hand. So far so good. Only thing I may have to get the LBS to do is put their rear derailleur alignment tool on it, depending on how the RD acts when I get it hooked up.

Building a bike isn't that hard. I have tons of tools from auto mechanic work over the years, and slowly have built up a collection of bike-specific tools in the past 3 years.