If there is a recorded plat that creates a road or ROW I think that would be sufficient for the title insurer to issue a policy w/o exception for a lack of access. 

Isnt it sufficient using apps like Stessa or Avail or Rentprep etc etc?

Would having a highly insured property (1,000,000+ liablity) plus not being a negligent or slum landlord be sufficient and not require the use of an LLC? 

80% LTC is standard on ground-up construction, if they are using an experienced builder, have decent credit & the after-build value is sufficient, it should be a fairly straight-forward loan.The main problem I see with non-experienced builders trying to build is lack of funds, they will need 20% of project cost + Closing Costs + 6 months reserves.

.: I'm sorry to sound negative, but $25k is not a sufficient investment to get going in real estate. 

Assuming the leases clearly state a security deposit amount, the seller knows that the tenant will be wanting a refund when the lease ends (after closing) so should be an easy reminder that you need those funds credited to you at closing from them to refund to the tenant when needed.If the seller spent the tenants deposit, at least the credit to you at closing comes out of the sales proceeds (seller just nets that much less at closing) and assuming they have sufficient equity should not be a big deal.  

Quote from @TJ Dittmar: Covering the mortgage isn't sufficient.

There are good relations with the neighbor so this likely wouldn't be terribly difficult to pull off, but I haven't ever developed a property from scratch so I would definitely like the opportunity to partner with someone on this to help ensure the success but first I want to finish the smaller property to have sufficient funding available if it is needed.

Do some research on whether a single-member LLC (or LLC with spouse) will even be sufficient to protect you.

Duplexes are a little easier than 3-4 units with FHA since they don't have to meet self-sufficiency requirements.