Nelly's studio apartment was great for what I needed and a good value. The famous Istiklal Street is a short walk away as well as the Taksim metro station. There is a lot to see and do in Istanbul. I recommend using public transportation when possible. The Istanbul card is 10 Turkish Liras (TL). One-way trips on the metro and ferry were only 3.5 TL. For short stays, the best data package I found at the IST airport was at Wifist: 20 GBs of data good for 5 days for 190 TL (no phone number included though). I was able to easily use Uber to get a taxi to and from the IST airport (one-way price about 220 TL). BiTaksi is also a good taxi app, but you need a working phone number to set it up.
Entry Requirements and Information:
1. Tourist visa needed: https://www.evisa.gov.tr/en/
2. For COVID, have to get a HES code prior to arrival
3. Required to link HES Code to Istanbul card: https://kisisellestirme.istanbulkart.istanbul/
4. For COVID PCR test, Cihangir Laboratory near Taksim Square was convenient: https://istanbulwelcomecard.com/shop/covid-pcr-test-istanbul The charge was 250 TL and I got results that by the end of the day for an afternoon appointment
Happy and safe travels everyone!