Have you given your relator any reason to believe you might cut him out at the last minute after he's spent a lot of time on you?

Although the numbers are important (cap rate, vacancy rate, average rentals in the area, etc. as others have mentioned here), it's really not all about that exclusively--there's value too in just getting experience, particularly at your relatively young age, and learning and growing now by doing something might be better for you long-term than making sure you get the most fantastic, risk-free deal conceivable.In general, I think Hudson County is a great place to invest in.

I'd talk with a lawyer to make sure you really understand the law and if it applies.Once you have your answer, I'd have the lawyer write up a quick letter clarifying the law and then show that to your relative.

You want them out, but you don't want to fight a civil war for the next 4 months.So, in the meantime it's probably best to first have an uncomfortable conversation with your related tenant (RT) wherein you describe in detail just how much of a financial bind not getting the rent on time is putting you in.

Down payment: if you have the money and only your relatives will be on the deed, then you must transfer this amount to then and it need to stay at least 90days on their account so you'll avoid questions like "where this money came from"2.

So if a hard money lender will lend you 75% of the ARV...and your relative is selling it to you at 80%...then you just need 5% down + closing costs to buy that property. 

Those are more important than your relative's purchase price.

Do you have a copy of the most recent lease agreement that the tenants and your relative signed in the past? 

If the lender is okay doing a hold back, you could close at the higher value, payout the contractors from proceeds after close for work completed up to that date, and or pay out on a schedule as work is completed like a renovation loan depending on how good your relations are with your title person.

If you can find the property at the right price with the right gross income to achieve your final net Income that would be great. there is no "standard" of what you should make, whether its a SFH or a 2FH. if you can make a profit, that is great, if for now the property breaks even, that's not bad either, that means it is being paid for by your tenants while the equity builds and that's happening without your money and most likely tax free ( especially if you keep it for your relatives to inherit). so do not feel you have to follow a specific "Rule".