I would have commented on another answer that is missing a bit of information, but as I lack the required reputation, I'll post this as a new answer.
It's 100% possible and allowed to sell physical goods or services in an app released on both iOS (via Apple Store) and Android (via Google Store), but the main difference between selling physical good or services and digital goods comes in the payment system to use. Both platform actually have 2 payments systems with, each, their own restriction and legal implementations.
In the case of Google Store (a.k.a. Google Play), it's as this:
Any digital purchases that adds anything into the app itself must be done through Google Play In-app Billing system. To put it simple, this is the typical in-app purchase you see in any game that charge onto the Credit Card registered by the user on the Google Play account.
Any Services and Physical Goods that are not set toward in-app usage have to use either your own version of a selling system (which has to be separated from Google Play In-App Billing system) or, if you want an more secure way, by using the Google Pay API.
The Google Pay API is really similar to the Google Play In-app Billing system as it allow any user to also use the credit card registered to their Google account (note that it's not Google Play, but a general Google Account), but the main difference is that the Google Pay API can also be used outside of an App (like on a website).
An example of stuff you must use the Google Pay API and NOT the Google Play In-App Billing system is to purchase physical goods (which requires a shipping address to be registered with the sell of goods) or services (like paying a rent of a room at an Hotel or the purchase of plane ticket, digital or not).
Here's the link toward the Google Pay API official website: https://developers.google.com/pay/api
For iOS and its Apple Store, the same equivalent exists, but the problem comes from the fact that both methods uses the same base system called Apple Pay.
For sells of goods and services, you need to address to the site "for merchants":
https://support.apple.com/HT204274
https://developer.apple.com/apple-pay/
For digital goods that are accessible directly through the app itself, you got to use the In-App Purchase system which is described here:
https://developer.apple.com/in-app-purchase/
There's one important thing you got to remember: Both stores might have some resistance to the idea of publishing an App as an App and as a Game. Both payment systems have their own rules and guidelines and, as such, if you are to put both a in-app purchase and an option to sell goods and/or services, both has to be visually separated and must NOT be mixed from one to another. For example, they might refuse to publish a game that has only physical goods to sell or an App in their Store app that is more of a game with in-app purchases and barely any instance of real-good purchases.
The cost of using either Google Play In-App purchase or Apple Pay In-App purchase is 30% of the sales.
On the other hands, Apple Pay for merchants (physical goods & services) have no additional cost from the credit cards issuers' fee which is usually around 3% to 6% based on the payment methods. For example, if the user is using Paypal to pay on Apple Pay, it's 2.9% + $0.30 USD per transaction. Direct Mastercards and Visa users might pay up to 6%. This is done and managed directly by Apple Pay.
Google Pay (for merchant) is also free and come with a fixed percentage rate of 2.9% per sales with credits cards and, in some countries, offers free transaction for direct-bank-transfers and debit cards.
In both cases, there's a limit per transaction. Google Pay has transaction limits, but their depends on the shops and user (shopper) data. I have seen the number $10,000 often as a limit per transaction.
Apple, technically, has limits or security based on the country where the purchase is placed. (All numbers are here: https://support.apple.com/HT207435 )
You may not use In-App Purchase to sell real-world goods and services.
, i.e., I can sell them through my e-commerce and I don't have to pay Apple. Is it correct? – Shirk