1. 90 day limit on stays
2. Health insurance requirements
3. Proof of funds test at UK borders
4. Pet passports
No doubt the EU will reciprocate.
Good luck with retiring to Malaga.
Try Mabletherpe instead.
However its reasonably clear what will happen.
Spain will apply same rules to Brits as they do to current 3rd country nationals, ie they’ll weed out the poor ones with income requirements.
Spain likes tourists. Most countries do - they spend a lot per day. Spain also likes rich foreigners - they bring wealth & few costs.
Spain tho isnt going to be encouraging elderly British couples on a depreciating £ pension of £15k & less who can barely afford a 2 bed flat.