They certainly can be. but if given proper rules, training and socialization, they're awesome dogs. I rescued a 6.5 year old Doxie who is deaf and sight impaired, with major resource guarding... it only took 4 weeks to cure him of it using positive methods only.
Some advice for you
1- never take anything high value away from your dog, (trade them for it), that leads to resource guarding
2- make your new puppy work for everything it considers valuable (petting, couch time, food treats) make him/her sit, or lay down or shake etc.
3- do not force train, or use dominance methods on your pup, it will often lead to behaviour problems and/or fear
4- socialize the heck outta your pup, pass him/her off to people for a cuddle, hand them treats to give her/him, let him/her play with other dogs, but make sure they dont hurt him/her expose the pup to many different situations, and give LOTS of positive feedback for appropriate behaviour
5- protect the pup's back, do not let him/her go down stairs or jump off of furniture.
6- lots of regular exercise, starting with short walks when really young (approximately 15 mins for each month of age after 2 months is all they can handle)