Cost of additions to existing structures in San Diego

[Ross A.]

Hello fellow San Diego investors. I've always bought turn key rental properties but this time I would like to explore adding three more bedrooms and 1-2 additional baths to an existing 1000 sf house with a 1.5 acre land. But I just don't have any idea how much it would cost to have these additions. Assuming I can get a permit and an engineering design to do all that. All ideas and feedback are welcome - thanks in advance!