A locksmith can sell you any number of locksets which all use the same key.
You can also get padlocks which can be changed to use the same key as the
house key if you have "schlage" locksets.

I have one key (same) for front door and deadbolt, back door and deadbolt,
gate padlock, and shed padlock.

Also you get what you pay for. Locksmiths sell "commercial" grade locksets
for around $200 which will pretty much last forever when used on a home.
These are designed for heavy use doors like schools, businesses, government,
etc. They do not sell these in home improvement stores.

I figure you pay the same over time. Replace cheap locksets every so many
years and the cost adds up. Or pay now and no need to replace in future.

observer wrote in message
My wood front door has polished brass handleset hardware which uses
the same key as the back door which has an entry knob & single
cylinder deadbolt combo. Since the polished brass is peeled due to
weathering (mostly hot sun), I'm thinking of replacing it with the
same (if possible) but if I replace both front and back door hardware
simultaneously, can I get one key for all (like the old ones are) or
do I need to get a locksmith to rekey both doors to use one key? I
don't know if I can buy a complete front/back door hardware set
similar to the existing in one package so that they share a key?

If I need a locksmith, any idea what this costs? Maybe not worth the
cost for the convenience of one key?