@Teho Kim That's an area that is changing.. At this point it's pretty speculative.. You didn't list whether it's a 1, 2 or 3 bedroom per side.
Worst case scenario:
1 bedroom duplex should rent for $450-500 per month
2 bedroom duplex should rent for $500-550 per month
3 bedroom duplex should rent for $575-650 per month
In Indianapolis: When dealing with multifams, you need to be aware of a couple of different things.
Higher vacancy rates, instead of 2-4 weeks to fill a single fam, you are looking at 4-8 weeks to fill a multifam. It’s not for lack of applicants, but lack of GOOD applicants.
Higher turnover rates.. While my single fam renters generally rent for 4+ years on average, my multifams only rent for 1-2 years on average. The premium for single family houses is not that much more, and most residents will gladly pay that amount to not have neighbors. Turns(One tenant moves out and you have to prep for next tenant) are what kill you in rentals. A good tenant turn is probably going to run you $1000-1500. It's VERY rare that someone gives you the property back in the same condition you gave it to them.
Watch out for owner paid utilities. These can break the deal. While water/sewer is easy to deal with($50-60 per month per unit), anytime you are paying for heat you are looking for trouble. Residents crank the heat up in the winter and then open a window to cool off...
Most multifams in Indy are in low income areas, and are much older(1900-1950’s). The deferred maintenances wrack up quickly, and you have to multiply that by the number of units.
I am not trying to scare you off, just you need to budget for them.