Is the asteroid coriolis a safe bet for building? It's not going to suddenly turn into x selling y when I finish it? I really am trigger shy at this point in the colonization game.
edit:
Also, do I put it in the first slot orbiting the gas giant I plan on mining at?
My experience of building an asteroid base as a non-primary port was: (Note, this occurred roughly a week ago with construction finishing on Saturday or Sunday, so things may have changed.)
3 slot ringed moon with 2 orbital slots.
I selected orbital slot 0 for the asteroid base. (My understanding is that the UI limits asteroid base placement, but I was very careful nevertheless.)
The game placed the asteroid base in a new slot between slot 0 and slot 1, both of which are empty.
The asteroid base spawned with 115% extraction economy. Apparently it did not inherit the tech level of the system, so Universal Cartographics was offline even though the main port in the system had UC online after building multiple tech buildings. The asteroid base did come with a reasonably well stocked shipyard (14 ships) so it probably sees some sort of development level?
I then built a refinery hub on the moon's surface. The refinery hub did not affect the economy of the asteroid base at all.
I decided to wait until weekly downtime to see if the construction clean-up helped. The construction site did get cleaned up but the asteroid base is still in a previously non-existent slot and still does not appear to see the refinery hub.
It is possible that building further hubs on the moon or building, say, an orbital in slot 0 might connect the asteroid base to the moon economy. Or it might just be bricked.
Imo extraction economies are not useful for further colonisation. Having orbital locations that will probably (er, might?) influence the asteroid base is very important to possibly having it be useful.
I don't think that I would build an asteroid base on a gas giant which only had one space slot for development.
However if you really like asteroid stations, it does seem to give some decent bonusses.
Edit: Also, during construction of the asteroid base, about 25% of the time it would drop me out of supercruise 40-50km away from the construction site. This is actually a super annoying distance because if you re-enter SC there's a delay before you can drop out again so I often ended up 20-25km away on the far side and had to slowboat to the dock.