Here is my advice if you decide to go for it.
It's not easy. It's not quick. Keep your non-aviation options open in the back of your mind in case things go south.

While you may not be able to log it, you can still learn. I have spent a buch of time in a right seat just watching, and it truly prepared me for the time when it was finally up to me to make the call.

Don't misunderstand----you have to build time. However, if this is a means to an end to build some quality time----it may be worth it.

Check it out, and ask questions. See if there is an oppertunity there. If so, show that you are a willing to work. Do the P.I.C., as in Papers, Ice and Coffee. Help clean the airplane. Ask "what can I do?" Be respectful, keep your ego in check, and try not to step on toes. Study the airplane, and ask questions.

Many people, even if they are single-pilot qualifed, will have you do radios and checklists, and give you things to do. That is a good thing for the reasons above.
If they truly only want a seatwarmer, where you do absolutely noting but sit there and do nothing but give the appearance of crew, that is not good.