Long term rental

Roz.  I recently took up residency in Algarve after taking a few weeks to look around areas to consider.
I have rented for 6 months Jan-June inclusive but found it exceedingly difficult procuring a long term rental in low season....Just like the Spanish , it appears the Portugese preference is to leave property empty for 9 months to make money in 3 months high season. Seems strange to me - Why not have both??!!
If you are looking for 3 months high season then it may be exceedingly expensive even if you find something. Rents can easily quadruple in high season.
My understanding is that part of the issue is that taxation is heavy for longer term rentals.
Also, if looking, please take into consideration the time of year....some areas can be virtual ghost towns for months during winter yet appear ideal if you visit in April or May...
I would check estate agencies but my finding was that almost none had or wanted rental business and those who did were looking for a month deposit for somewhat disappointing properties.
I eventually found a rental option in a perfect location for me via word of mouth.......we asked the owner of hotel we were staying if he knew of anyone...and we were introduced to another member of the family who had a property but had not previously thought of renting it other than in the summer months.
So far it has worked out just fine and wish you luck too.
Ps.  If you are looking for a double room in a large 3 double roomed apartment, central old town Albufeira 400yds from beach and restaurants but in a quiet area meantime or Jan-June 2020 then I may have just the ticket!!
Best wishes. Alan