[Strontium]

Hi and Welcome,
Part1:
I'd suggest you do two things before making any decisions. - first spend time here in different places at different times of the year, what seems a pleasant sunny spring day can also be a damp/moldy in winter and oppressively hot in Summer. Whilst here look at property to rent/buy, there is a general lack of rentals available whereas buying land (generally no building on Rustic land and only places Habitation licence or exemption can be lived in ) and building new here is a MASSIVE nightmare. You can buy property without being a resident, ie using a UK address to first get NIF (tax number) then Portuguese bank account, you can do both of these yourself when here. Property for sale main sites are OXL PT and Idealista PT. NHR has sort of stopped but there;s also some talk about it may change yet again.

 

[Strontium]

Part 2:
Pre 1953 (?) houses have an exemption for habitation licence so buying an "Ruin" which is registered as being older is usually a way to rebuild onto the footprint with similar facade/window size. House has article number on the "land registry" which you or estate agent or lawyer can access and has floor area etc. Obviously you may see where someone has extended without permission so good to check "land registry" listing.

https://www2.gov.pt/en-GB/web/guest/servicos/pedir-uma-certidao-de-registo-predial

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House with garden is usually two articles with garden classed as "Rustic" so can't just extend house, not everwhere has easy access to mains water, or main sewerage, only about 10% have main gas. New build will need to be the latest building regs but rebuilds are more flexible. Land may have been under declared in the past as it gets taxed on the area - think someone calculated the total land on the"land registry" is 8% smaller then the area of Portugal. Inheritance here is the estate gets divided equally amongst the offspring ( and their offspring if pre deceased) so property may have many owners who all have to agree to a sale - sometimes a lengthy or impossible process, the rural areas may have had plots sub divided over the years and no one knows where the boundarys are.
If you start looking at places maybe get a Portuguese phone sim (airport arrivals shop) for your two sim phone as people don't like calling " foreign numbers". One part of buying/sell property is the Promissory Contract (contrato de promessa de compra e venda) where the buyer and vendor sign agreement and buyer puts up (usually) 10% deposit which they lose if they dont follow through, vendor (usually) has to pay 20% if they don't follow through, contract usually have property discription, vendor and seller details, agreed price, date of transfer AND anything else either wished to include in the agreement like like vendor to remove old caravan, repair front window, reinstate boundary fence, update land registry listing of garden .............

When you've posted a few moree I think I can message you direct with link to a recent discussion involving land/new build. There is also an issue with getting information from offices/councils/builders/lawyers/estate agents where the information is not consistant.