You can buy an off-plan or a ready property. Off-plans come with payment plans (sometimes extending after handover). Be very careful to pay in time, if you fail you will face fines and a potential loss of every penny you invested in the property. You can sell an off-plan when you paid at least 40% of the price, however many developers demand at least 50%. Keep in mind that you also pay 4% DLD (property tax) when signing the contract, but you don't pay an agent (they are paid by the developer). Some developers accept payments in crypto, cash, all of them accept checks and wires.
When buying finished objects you will pay an additional 2.1% agent fee (it's almost impossible to avoid unless your agent wants to share his payment with you which is very rare). You can pay with a manager check, there are many ways to pay in wire, crypto and some ways to pay in cash, so technically you don't need a bank account in UAE.
You also need to pay a 2000 AED deposit to DEWA (water and electricity company), can be easily done by a credit card.
You rent through agents usually, pay 5% of the contract price, they collect checks and help handle the maintenance. It's usually hassle free, however be prepared to allocate some of the income towards refurbishment and refurnishing.
Depending on the area and the type of the property, rental yields will be 3-9% gross, a bit less after fees. Villas yield less, smaller properties yield more, cheaper areas also yield more, but amortisation is higher, so need to do the math on the long run.
You can change the rental price annually according to RERA index.
Rent is usually paid with checks (1,2 or 4 checks are the normal, 12 checks are unusual but happens). More checks = higher rent (time equals money). You will also receive a deposit that can be (partially) used for cover the damage when the tenants move out (1-2 months of rent). You will need a UAE bank account to cash the check. You can agree with the renters to accept payments in cash, just don't forget to register the contract with rera.
It's NOT easy to open a bank account in UAE. If you have a 2m+ AED property you can apply for a golden visa and it will significantly simplify things, however even with EID and a local address it's a pain in the arse if you are from "risky" country. One of the shortcuts I personally saw is having a HSBC Premier account in your current country of residence and just opening a UAE one as an existing customer - takes a day or two.
