Salary of Euro 90000.

This is a very good salary by German standards.
Whether his wife can work (and can find a job) depends on too many factots to speculate here.

Why are you writing in third person? There is nothing to be ashamed about.

Thanks for reply. Well I am not ashamed but seriously asking for my friend.

What do you mean by very good salary as per German standard. I heared that in Germany one has to pay 40/45% taxes.
Just wanted to to know whether woth euro 90000 what would be monthly take home?

With "very good salary" I meant that it is more than usual for such position (and far above average German incomes).
German tax rules are very complicated and his take-home pay depends on many factors - he should ask a tax consultant about this. The 40-45% you mentioned probably include (compulsory) insurances for health, unemployment and pension plan contributions - then the number is probably correct.

I have a wife who doesn't work and we raised her son never having earned even half that amount. So it is a good wage, more than the average German, as long as you don't expect to live in a mansion and drive a Porsche. Probably the biggest factor that might reduce the attractiveness of such a wage for a foreigner is if the child has to go to a private school that gives instruction in English. German public schools are free and generally quite good but taught in German. For a long term or indefinite stay it is best a child learns German anyway and thus they could go to a public school. But for a shorter stay or temporarily until a child gets their German up to standard, such a private school might be necessary - and generally cost 12 to 18 thousand euros a year. This subject has been discussed in detail here on other threads.

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That is more than enough. With his wife not working he can apply for class 3 tax card which will lower his tax rate to under 40%..

Average salary in IT with that experience is 60k. 90k is usually for managers and sometimes offered for people relocating.

Yes private schools will take away from that but you will still have a very good lifestyle. Food is cheap here and flat rentals at least compared to Canada.

If he applies to class 3 he will net around 4800 EUR a month after all deductions.. If he applies as class 1 ( single) probably around 4200 EUR..

It also depends on the city you live in.

There is a misconception about German tax classes above:
How much tax you pay in the end does NOT depend on your tax class - the tax class only determines how much is deducted at source. The actual tax bill depends on your whole year income (and many individual factors, but NOT the tax class!). It is calculated after the end of the year when you submit your yearly tax declaration, and you get back (or have to additionally pay) the difference then. The tax class thus only determines if you give or receive an interest-free loan to/from the government due to the difficulty of calculating the individual tax bills correctly during the year.
If you don't understand the German tax system, you are not alone - most Germans don't either. Get a good tax consultant!

what do you want to know? If a salary of 9000 Euro is enough? This is 90 00 Euro per what? Per Month, per year?
And enough for what?