If you are strong, shotgun. Mossberg 88 12 gauge - same as a 500 but $200 less b/c some trim parts can’t be replaced.
If you aren’t strong, a weaker shotgun - 20 gauge or 410.
In either case get one that can hold 7-8 shells. Semi-auto may also be a good thing to consider, but stick with higher end brands for reliability and safety. Winchester makes a good semi-auto home defense - 930 SPX.
People poo poo the 410 all the time but 5 .30 cal balls going 1150 fps is nothing to sneer at.
Let me ask you a question....I inherited my dads 38 special colt cobra that he used with his cw permit after retiring, used a shoulder holster..your opinion of that gun? GG