Do cracks in a brick wall signify a serious problem?
The bricks separating from the threshold is a cosmetic problem, but it is a symptom, along with your cracked mortar and bricks of something more significant -- the foundation is/has settled. You should ask if the foundation (this typically occurs with slab vs. pier and beam) has been repaired. If done recently, then you have some &quot;minor&quot; fixes for the cosmetics.  If the foundation was repaired some time ago, or hasn't been fixed, then you should get a professional to inspect it, assuming you can get access to inside of property.
I've had this issue with two properties in the DFW area, and both times the foundation repair was approx. $8000 to $9000, which was on the low end of estimates.  That work will only fix the foundation, and it will only last as long as the owner keeps the soil watered around the house afterwards, for as long as the owner has the property. it is a result of the shifting clay soil found in the DFW area.
I had a bid to fix my cracked mortar and bricks, and the estimate wasn't too bad, but it wasn't really too large of an area (maybe $500 IIRC?). It included being able to match the color of the mortar, which (for me) was critical. I fixed the bricks at the threshold myself for practically nothing.
If the house has had foundation repairs, but the owner didn't keep the foundation watered, as we say, then there's no reason why the property couldn't need additional foundation repair.
Built in 2018? That's a relatively new home and it suggests how bad the soil is in this area, as well as suggesting how little care was given to the landscaping/area immediately around the house, since it's already messed up within less than 3 yrs.  should you pass? Depends upon your budget. The vast majority of residential properties have/had this issue in this part of Texas.
Will it last 5 to 10 yrs.? maybe, assuming the foundation is/will get repaired and how extensive the cracks in the mortar are.  I have seen similar brick walls still standing after that amount of time.  Obviously, if you buy it, you will want to fix it- either now or when you go to sell it in the future. the cosmetics won't necessarily keep someone from getting financing for the purchase, but needed foundation repairs can prevent financing.