Who hires who..

When you hire a model, you're doing it for one or more of a few reasons:

- the model has a look you need/want for your port
- the model has the experience you need/want for your port
- the model has a skill you need/want for your port
- the model has a "name" or such that would benefit your port

There's probably a few more reasons, but those are the most common.

When a model hires a photographer, it's for one or more of a few reasons:

- the photographer has a look you need/want for your port
- the photographer has the experience you need/want for your port
- the photographer has a skill you need/want for your port
- the photographer has a "name" or such that would benefit your port

When a client hires a model/photographer/team, it's for one or more of a few reasons:

- a look in need/want for their project
- the experience in need/want for their project
- a skill in need/want for their project
- a "name" or such that is in need for their project

When both parties work trade, it's for one or more of a few reasons:

- a look both parties need/want for their port
- the experience both parties need/want for their port
- a skill both parties need/want for their port
- a "name" or such that would benefit both parties' portfolios

One should always strive to "trade up" when working trade. PYPI can expunge on this in more detail.

It can't be explain much clearer then that.