I graduated from college with a business degree that had a real estate emphasis.  

I head straight to the mechanical first...

I don't think I'm willing to give anybody $X,000 of money I can't get back if I can't inspect the property.And what are the mechanics of the transaction?

I have full time mechanical engineering career that lets us save some money every month.

(emphasis added :)Good luck

If the house is affordable, since it was built 30+ years ago it most likely needs all new mechanicals and then becomes too costly to repair and still be affordable or has some major costs in the near future.

Are there mechanical issues coming up you don't want to deal with?

You can get this by involving other investors, but if you're trying to maintain 100% ownership of all your properties, you have to have some money to bring to the table to start the BRRRR cycle or whatever other mechanism you are using to make profit and cash flow in real estate. 

If you need to upgrade the mechanicals ( electric panel and/or wiring, HVAC, rough plumbing, etc)- I would hire the specialists to do their trade, then a drywall company to close up the walls.

In terms of rehabbing the property, the workflow can range from throwing a coat of paint on a wall or two, to an entire gut of the mechanicals, windows, siding, and flooring.