So ultimately this may require a discussion with counsel, and you may have to settle on splitting the cost.

These programs offer options for less money down and in some cases DPA - Down payment assistance.As a banker for over 18+ years I am very skeptical when I hear a new name in the business only because its become tougher to lend with all of the new laws and credit/insurance requirements and regulations.  

LIHTC properties can have requirements that stay with the property for up to 15 years.

That does not require employment or job seasoning instead it uses the rents to qualify and you can take out up to 80% LTV cash.Use the cash to put down on the next 1-2 or more properties as long as the other properties are debt servicing themselves it opens up more opportuities to buy more future assets and increase your passice income.  

You'll need more capital and most will require a personal guarantee and personal financial backing. 

How do you think the 2 relatives will feel about having their rent raised or being required to pay rent period?

google "all inclusive Deed of Trust" fantastic CA document we used all the way back in the early 80s If I'm not mistaken though a wrap would require the 2nd buyer to also agree to financing terms; which would be the same as me (the 1st buyer). 

Especially in a high interest rate environment where cash flows on long term rentals are muted and there is significant capital required to purchase and list on airbnb.I live near NYC but would invest out of state in an airbnb / landlord friendly state.

Majority of the houses are old and require frequent repairs in addition to a poor tenant base that can't pay on time and don't care about their credit.

There are also 'mezz' lenders (typically for larger transactions) who will cover up to 90% CLTV and require you to bring the remaining equity to the deal, and additionally there is Gap Funding in the form of unsecured personal debt.The latter can potentially be the most expensive option, but allows for true 100% financing as there are no restrictions for how to use these funds, as they are unsecured, and generally obtained through personal credit, income etc (since there is no collateral for obtaining these funds).