we are treating this as an investment and certainly don’t hope the price will be the same 10 years from now.
On the other note, we know a rental license is needed for vacation rental in the old town. The question is is the city really reinforce the rule?
Buying for investment in Spain is currently a very poor idea. Annual increases in capital value are no longer a given. In fact in the last five years values have steadily dropped. Why should that trend change in the medium term given the state of the economy? It could be a decade or more before capital values start to rise. This market and the Spanish economy are seriously damaged.
My best estimate is that in 10 years time your property will be worth exactly what you pay for it now.
The Spanish government see property, especially second homes as a cash cow. Property taxes are bound to rise. That includes none resident tax, council tax, inheritance tax, income tax. Rental income is taxable and you will have to pay it somewhere.
A rental license is way of ensuring proper taxes are paid. Why would you think it would not be enforced?