Another thread about buying first property. Would like some guidance.

[Steve Kim]

I found (what I think is) a good deal on a duplex in Billings, MT.

Asking $75,000 for a 3+1/1+1 duplex. I think I can get it for $70,000.

It is currently rented out and it brings in $900 in rent total per month.

It is in a relatively good neighborhood with two schools close by.

Based on the simple rule of thumbs (the 1% and 50% rule), it seems like a good investment with positive cash flow ($450 in expenses and about $250 mortgage)

Now with that said, how important is it to know the cap rate, tax, insurance, vacancy rate, etc?
If it is crucial for me to know those figures, do I just ask an agent to get me the information or do I have to go through the appropriate sources (ie county court, quotes, etc)?

I apologize in advance if this is a really dumb question. I'm just getting started in RE investing and trying to learn as I go.