Making an existing content type a field in another content type in Drupal 7

I'm still working my way up the learning curve for Drupal and I can't seem to find an answer.

I have created a custom content type. In my case, it describes an investment property (purchase price, rental income, etc).

I now want to create another couple content types: Expense and Income that will be used to track any expenses or income that apply to a particular property.

What I can't figure out is how to let the user choose which property an expense or income would apply to. That is, I want a field where the user can select the property.

Do I need to write a module 开发者_如何学JAVAthat makes the property available as a field?

Thanks in advance.

I think the references module might help.

http://drupal.org/project/references

I don't have extensive experience with it, although I thought I'd point you towards it. If it's what you need, I'm sure others with more experience than myself will chip in and help you out if you have more specific questions.