I would review the rents and the condition of the duplex prior to making any offer.

Is it being restored to like condition, or are they making other changes like color or style?

This is also presupposing that your current rent is at market rent and not already below it, at least to some extent.In a nutshell, can you find a different rental in the same area that is in a similar condition and has the same "perks" as where you are renting, but has cheaper rent. 

You then have to compare the properties, locations, beds/baths, amenities, condition, time on market etc to determine the appropriate price for your property. 

Here is an example:Yesterday I wrote an offer for a $40k house in good but not updated condition, in a solid C neighborhood that's currently rented for $875/month by a lady who's paid 2 months ahead.

It all depends on the area, type and condition of property, the tenant mix, your expertise and financial strength.

This is one of many reasons why NOI divided by cap rate does not really work.Typically I am modeling various capex spending across the years, i.e. the property condition assessment outlines $200k of issues, $100k is needed immediately, $50k yr 2 and $50k yr 3. 

Pay attention to price and condition.

We buy them in poor condition, fix them and refinance.

I renovated a few things on my own and increased rents to market levels depending on condition of unit.