As far as savings/down payment, it is probably a good idea to have a emergency fund buffer beyond your down payment.

You have a general idea of what you are looking for but those are 3 vastly different markets with variations in pricing and inventory.

Ruchit - Here are some ideas for that couple. 

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Regardless, if you do rent to them via Airbnb you'll want to properly vet that guest and make sure they have a state-specific lease and security deposits.

My tenants or anyone else for that matter, have no idea my LLC actually "owns the property".

If you want to maximize your max rents then if might be a good idea to condomise it so that you can get rents as two separate units.

But, sadly, I think that if you posted this for sale out in the real estate investing world, saying you are open to seller finance at 0% interest, you might have an incredible amount of interest, and be able to take advantage of many newbies who have no idea what they are doing. 

However there is the potential for downstream liability in the event the GC does not properly paper contracts with sub contractors and those same down stream subcontractors aren't insured.

One possible idea I had was working a new deal with seller for 50% less than the original deal on the recorded paper and separately give seller cash once I build and sell new home.