I've seen a bunch the were toast from the seal failing or the vinyl breaking down over time.

People that want to get in a house and do nothing but live in it are usually willing to pay a premium for a turn-key, tight-sealed, and packaged home.

We designed our plans off of that, a month later after the plans where sealed we found out that the easements had been changed a few years ago and where on a different plat. 

Now it just says sealed.

@Doug R.I can't give you a number, but things that you should factor into maintenance in a concrete building in PR are: sealing roofs and yearly maintenance of the same; kitchens (depending on quality 5 to 10 years); paint (about every 5 years).

Its of no benefit to me to seal a deal and then a month later at the closing table have everything fall apart because of an exception on the title report...I'd rather catch those issues before spending the time showing a property.

It is an absolutely true phenomenon that can easily be maintained as long as the brick is sealed every few years.

Not a deal breaker because sometimes its a 500 or less seal job , other times its a 10k wall anchor or hydraulics some foundation problems can create great opportunity because the general rule is "stay away".  

But this can be repaired and sealed.

If you were to stick-build to a high efficiency (i.e. offset wall with no thermal bridging, proper envelope sealing, and substantial thermal mass on the inner walls), your cost variance to a modular built home will be much smaller.