phrasal verbs mix - came up with; set up; join in

[Jon]

Hi again,

Sentences
-s1- He has ____ a business that sells technical support on the internet

Issues
-i1- I understand that the meaning of the next phrasal verbs are:
came up with = to suggest (for example a new idea, os business)
set up = to create, to prepare
join in = to participate
Please take a look to these meanins in case they are wrong and share comments
-i2- which one fits better in s1. Are the rest incorrect in case of being used?

One more time ... thanks in advance !!

[Mister Micawber]

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'Set up' is the answer. We 'come up with' relatively simple ideas, not businesses. We do not 'join in a business'; we 'join a company'.
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Native English teacher at Mister Micawber's