nice stay in 10-15 minutes from galata tower and istiklal street. engin is a very helpful host, gave me instructions how to get the appartement from the airport, met me as soon as i came and even left me istanbulcard with some money (such a bonus!).
be cautious that there is no separate place and room for shower, the shower is combined with toilette so don't expect much from the small bathroom if you are used to big bathrooms.
don't forget you have a chance to cook at the appartement with all local products : )
and please find a time to visit karaköy and moda coast.