As we understand it, it's common to go there on a 90-day visa and look for a job, and then obtain the proper permit.
This is correct if you are an EU/EFTA citizen, sort of. For this you need an L-permit. It is likely you will be asked to prove you have sufficient funds to support yourself:
Since 1 April 2015, citizens of European Union (EU) or European Free Trade Association (EFTA) countries seeking employment in Switzerland can only obtain a residence permit if they have sufficient funds to support themselves.
An L-permit is valid for a year, usually. I suspect therefore you will be required to prove you have sufficient funds to live for a year in Switzerland (a student I know was asked to prove they have around 20,000 CHF). After this time, if you have a normal full-time job, your permit converts to a B-permit (right to reside and work). There are various other possibilities depending on your employment status and going through them all here would be impossible.
To be clear, everyone in Switzerland who has accommodation is required to announce themselves in their local commune on arrival within 8 days, including the Swiss. This is because tax liability (and actual Swiss nationality) is divided between commune, canton and the federal state. As such, as soon as you move and register your arrival, the process will start and you'll be issued an L-permit.
So that covers your wife. :) As a US citizen you do not need a visa for a 90-day stay but you do need one for longer than that (and a residence permit if you reside). However, according to expatica, if your wife has a permit of residence in Switzerland you are also entitled to a permit and may join her here.
I am not sure how this would work if you are moving on a short-term basis without a job and I cannot find much info online. I belbieve that if expatica is correct, you will be treated as an EU citzen. ut without explicit confirmation I think that the best thing to do would be to talk to your nearest Swiss embassy or consulate, particularly as they can explain what (if anything) you might require. If you are in Switzerland, you can talk to the cantonal authorities in your region. They should be able to give you a clear answer.
Various comments have mentioned a vote in 2014. Said vote was the "against mass immigration" initiative, which requires the federal government to re-introduce quotas on all foreign nationals entering Switzerland to live, including EU citizens. This is obviously incompatible with the Schengen treaty and quite how it will all work out is entirely unknown. There are counter initiatives working their way through the Swiss political system and Swiss-EU negotiations are currently stalled waiting for the outcome of Brexit. The vote was contentious in Switzerland itself (won by a very narrow margin) and a recent vote to automatically deport foreigners who have been imprisoned once their term is over was more thoroughly rejected.
The previous answer mentions the tax situation. As a resident of Switzerland you must pay tax on your worldwide income. As both you and your wife are US persons you will also have to (potentially) pay tax to the IRS. As I understand it, you must calculate your tax liability with the US and then you pay the difference, taking into account your tax burden in Switzerland. This would apply no matter where you moved to live in the world. I am not a US person and I'm sure there are more detailed answers on the nuances of this around the site.
