How to evaluate this dilapidated foreclosure multifamily property

[Edward Yu]

This is the property in question. I'm not going to bid on this specific property, but wanted to get feedback on how to evaluate capex costs for a property with no access to interior. Back of the napkin math:

Nearby fourplexes selling for around $200k. Rental income somewhere around $650 x 4 = $2600 / month. Pretty solid cashflow. Now the big elephant in the room is that the listing price is $76,960, BUT there's no access to interior. So how am I supposed to figure out what the cost would be to get the property in rentable shape? Anyone with experience in rehabbing foreclosures have a ballpark estimate?