First of all I wouldn’t use Ionic 4 as it’s in beta version, meaning it’s not stable and buggy.
Answering your other questions (which just need a bit of Google):
- That can’t be answered as it depends on how good the programmer is.
- Plugins like
Geolocation has methods to continuosly watch for the location, that and a Maps service will do it (you can’t use Google Maps as they don’t allow in their license to use their services to make Apps like the ones they already have, so you’ll have to find something else than Google Maps).
- That depends on what you want, if you want PayPal then use PayPal’s services, if you want more payment methods then you can use something like PaymentWall or something similar, or maybe talk to your bank to use a TPV but that will only allow to pay through credit/debit cards.