Offer Price advice

[Anthony Santa Ana]

Needed some advice about an offer price. Here is the situation:

-motivated seller that is willing to seller finance and/or lease option
-asking price $595,000
-3 duplex houses on one lot (2 units rented out for each @ $1175-4 units vacant with potential of $7000)
-separately metered
-tenant yearly leases
-one house needs a full rehab (interior & exterior)
-$4596 yr=taxes; estimate $1200 yr=insurance
-seller ok with 10% down
-zoned for commercial & residential

Any suggestions or ideas. Any advice is greatly appreciated!