Is there a requirement for such stuff where a co-founder actually have to invest a proportional amount of money when setting up their startup as a business/company? What if they just come with ideas/technical skills and the other guy comes with money? What is the usual rule for this?
It is not necessary.
Co-founders doesn't necessarily mean proportional equity. And as we all know it rarely means proportional work!
The critical issue is that the members of the business/company feel comfortable with the details of their relationship. Really. Not just they say they are -- but they are. Times are going to get tough and relationships are going to be strained. The founders need to layout the original equity, the sweat equity, the performance bonuses, the compensation.
The co-founders need to remove the doubt by having the conversation fully and documenting it on paper in a way that both of have taken ownership for their approval.
Nothing is necessary. A co-founder must ultimately bring value. However you do the math works. Money has value. Work has value. The problem is that it is like comparing apples and oranges, but in your heart of hearts (Shakespeare!!) you should know have a feel for who is contributing how much value.
It doesn't matter but there are a few things you should get straight if that is the case:
What is the value of what you are putting up if not money?
Is it your time... if so put a $ value per week or month. At some point you are going to want to say "we are even or I have paid my side". Agreeing this will help at the other end.
Share split guideline from our blog (cut and paste):
We typically have a few standard metrics we use to run through how much a share is worth:
Employee shares is the outlier here, for key staff you want to reward them ... either they get split under each of the headings above and are a part of those shares or they are a seperate block ... around 10-15% is reasonable to balance incentive against dilution.
A few notes about these splits
See also (from our blog):