The only time I'd say it's an okay idea is if either: The area you're investing in is expecting so much appreciation that you will easily profit off that (watch out for mortgage interest though...the appreciation needs to be higher than what you pay in that and expenses to make it profitable)You have some specific reason for wanting to do it- family ties, future home, major long-term hold, etc.Maybe I'm forgetting another one, but those two are all I have for now...

It’s in pretty good shape at this point, rentable.I travel a lot for work, and a friend gave me the idea to do a short term rental as a one bedroom, locking all of my stuff in the other bedroom and office - I applied today and was denied because I don’t own both sides of my HPR, even though I have written permission from the owner of the other half….

any ideas if there are any builders who would sell it to investors like me who wish to add new construction SFH's to their portfolios ?

I have no idea, I am struggling to find the info!

Here are a few ideas to explore that might help you get closer to homeownership in San Diego without selling:Cash-Out Refinance:Refinancing one or both of your El Centro properties could free up additional cash for a down payment without selling.

I just think basement access is generally a bad idea.

I’d also love market suggestions and ideas regarding how to connect with others in the REI space outside of the events that BP holds.

Besides, it's always a good idea to build a good relationship with the Planning and Building departments. 

No, it's not a good idea, but it's possible to do correctly if you don't rush into it.

I don't think you're being too ambitious, I think its a very smart Idea especially in Chicago where there are an abundance of 2-4 unit buildings!