I own 4 duplexes but not in TX. Mine are all relatively low end inexpensive housing so they won't compare to a really nice high end duplex.
The rent vs purchase price is pretty decent although my experience has been that my duplexes always lose money in year 1 and start producing cash in year 2+. So be aware of this going in. For some reason things break a lot more in the first year I own them.
Are they 1 or 2 bedroom units? Are they at market price? A duplex generally gets a little lower rent than a freestanding house unless it is really nice.
Do all the utilities have separate meters for each tenant?
In my experience the duplexes have higher headaches, higher turnover and higher profits than my single family homes. If you are driving from Allen to Garland all the time, factor in how long it will take to get there because I have to run by my duplexes a lot. It got so bad that I finally handed all my duplexes off to a property manager and manage the single family houses myself because of the difference in workloads.
I am not scared of big dogs if your insurance will cover a German Shepard, but they will ruin the carpet and wood floors every time. I usually put ceramic or porcelain tile in the whole house and then big dogs are no problem. In fact it makes it harder for the tenants to leave as it is generally hard for them to find a place willing to rent to them. Also get a bigger deposit as the dog may ruin some doors by scratching. Check with your insurance company though as a lot of companies explicitly state they wont cover several dog breeds and German Shepherds are usually on the list.
Duplexes are great for cash flow after the first year, but go into them knowing they require more maintenance than single family.
