About net income showed in listings, should this entail everything except for my loan payment?

If you are talking about NOI - Net Operating Income - that would be what is left over after you have paid all typical operational type expenses - maintenance, utilities, taxes, insurance, management, etc. - and BEFORE debt service. Would not typically include capital expenses or tenant improvements.

Debt Service should not enter the scene unless one is figuring yield or return on investment.

As a word of caution, do not take the net income shown in most (not all) listings. With that being said, it is a great place to start. Good luck.