The issue is you do not own a home, so unfortunately the GC's do not know if this is just an exercise or not. Estimates take a lot of time, especially old house and there can be many unknowns making it almost impossible to give you an accurate estimate without actually being in the home and doing some probing and investigating. Also as they say time is money. You could offer to pay without the specific house a house specific game plan it is virtually impossible to give anything more than a wild a** guess.

If you're having this much trouble getting an estimate, imagine how difficult it is going to be to get the contractor you want to do the work.

Someone in the area has built a few second stories recently and will have a seat-of-the-pants square foot price. You'll be lucky to get your phone call taken; you're not getting a 5-page detailed proposal for something that may not happen for free.

You are wise to get some cost information to inform your purchase decision. Once you've selected a home, I suggest you make a purchase offer contingent on a study period of say, 60 days (I know this won't be possible in some markets.) During the study period you can get some concept plans for the remodel produced and costed out. Be prepared to pay for the design and cost estimating. The remodeler doing the estimating may be willing to credit back the cost of the estimate if you move forward with their company to do the remodel.

Best wishes for a successful outcome.

FWIW I used to have a contractor who was willing to come with me to look at houses I was contemplating buying and renovating. I paid him for his time to walk through with me and comment on feasibility and ballpark costs for things I was considering. But I never expected that as a free service- I was always respectful of the value of his time. Honestly for your purposes I would assume at least 150% of the cost of new construction on a per SF basis, because you won’t just be adding on new SF but also updating systems to bring things up to current code. So if construction is $400/sf for mid-range finishes in your area I’d assume $600k for a 1000sf addition as you go look at properties and assess feasibility. Crude, yes.

It will cost you the entire cost of the old house you tear down, plus the cost of the brand new house that has to be built. So youll need to have a very flexible budget, and very flexible bank. Looks to be about 3-8M total. And 3-5 years of time to jump through all the designing and red tape required .

8 million? Seems a little high, lol.

Depends on aquisition costs, carrying costs, financing juggling, how close to the beach, and the finish levels. Acquisition costs are in the 1-2M category, and a new build is 2-5M, depending on size and options. Add on 2 years of planning and paperwork hoops, and cost increases.

Older 1 bathroom type home acquisition costs. https://www.zillow.com/homedetails/417-Avenue-E-Redondo-Beach-CA-90277/21323636_zpid/

New construction. Across the 1, closer to the beach, the price only goes up. https://www.zillow.com/homedetails/544-S-Helberta-Ave-Redondo-Beach-CA-90277/21320562_zpid/

What Chispa said.