Is this deal worth the investment.

[Jeanette Christmas]

I found a duplex I want to invest in, it is in the rough part of town and need a lot of rehab. There are tenants and it rents at $800/ unit I was wondering if offering $40,000 cash is a good bet from FSBO price of $62,000. ? I don't have funds so sale and rehab will be hopefully sourced from hard money. I'm am looking for rental income and potential cash flow for future RE investments. How can I calculate ARV? Because tenants are currently living there any recommendations on how I can rehab while occupied or should I wait until they move out? It's been on mkt for 87 days.