Flippers and Brrr-ers of DFW: Which types of projects do you like?  1-cosmetic (paint, new floors, maybe a few small framing changes), 2-some real remodeling/maybe a major system or two (new baths, foundation + hvac, ...

Contact the local county the house is in and they typically will walk/talk you through it. 

My question was more about if other houses that are generally referenced as  houses with an "in law" apartment would count as comps or not, as they tend to go much higher in price than the typical "duplex".

You can get a HML to purchase the property on a short term loan then refi out or you can find a lender willing to do a 30 year mortgage on the property as well it really depends on the scenario but occupied properties aren't typically an issue as long as the occupant isn't the owner

Typically yes the interest payment is calculated on the principle so it should lower the payments but probably not by enough to make it worthwhile.

Many of the places we saw were what we associated with typical student rentals - old houses in fair to poor condition, with students sandwiched into small rooms and ancient common areas in serious need of updates.After much searching, we came upon a nice 5 bedroom brick home about the same 10 minute walk from our daughter's main classroom building as her freshman dorm. 

Multifamily are typically produce better cash flow but a good deal on a SFH can out perform a multi. 

As others have said, typically NOI and a resulting CAP rate on determines the value on multi-family properties, which are defined as 5+ units. 

However, they typically cannot owner occupy. 

I can tell you from experience underwriting deals for a number of institutional and semi-pro investors that they have achieved IRRs greater than 15% and yields greater than 8% in markets like San Francisco, LA, NY, and DC that advertise 4% cap rates.Markets with low cap rates typically share the following characteristics:1) Strong rent growth, driven by2) Strong population growth, driven by3) Strong job growth4) Low vacancy5) High per bed rents (lower operating costs as a percentage of total rent)6) Good property management options7) Higher quality tenants (young professionals like myself will rent in SF until their late 30s to early 40s)To achieve returns in these markets, investors buy buildings with significant value-add or development opportunities on very low to no leverage (debt), and refinancing the deal after stabilization to cash out.