Thanks for writing to us on AskGuru.
The most affordable areas to buy resale HDB flats are non-mature estates such as Punggol and Sengkang, typically far from the city centre.
Find HDB flats for sale in Singapore: https://www.propertyguru.com.sg/hdb-for-sale
Hope this answers your question.
You may text 9620 0827 for a casual chat. We can do an estimated financial statement to determine the affordability level which we have done for other clients in order to zero down to the area for affordability.
You can check out some statistics on the HDB website. I've given the link here for easy reference.
You can contact me at 8866 7000 for a non-obligatory discussion.