Like
@daniels27 said, you pay at least personal
income tax on the rent you receive.
Most countries want to know your
global income in order to calculate the correct tax rate, otherwise you could rent out real estate for e.g. 15k per year in every country in the world and not pay tax anywhere (assuming 15k would be below the threshold for income tax in every country).
So say 15k is under the threshold for income tax in the country where the real estate is located. But you also have income through your business of 1M per year.
Then you have to declare this and instead of paying 0, you have to pay e.g. 48% (maximum tax rate) on the rental income, since you are "rich", so 7.5k per year.
But not only that, now they know you have 1M and live in
Panama. This may or may not make them go: "Hmmm, I wonder if there is some way to tax this guy after all..."
Say you're from
Spain, where tax inspectors are paid a commission based on how much tax they can "get back". You visit your family a few times per year.
They find this out and just claim you really still have your center of vital interest in Spain and should pay tax on your global income in Spain. You have already declared you have an income of 1M and they send you a tax bill for 500k. Now you have to fight this and pay lawyers etc. - even if everything is perfectly clean you really live in Panama full time and you win in court, you still have to pay lawyers to make the case go away.
Now imagine you had given the real estate to your grand ma who lives on a small pension, 10k per year. She pays
no tax since it's very low income.
Gifting her the real estate is tax free since it's close family (you have to check your case, this is just an example).
Now she has rental income to top off her pension, 25k in total. She pays 10% tax on this, 2.5k in total.
She can then send you some money as a gift every month, and since you're saving 5k in taxes every year, you could even let her keep some of the money for herself and you'd still have more money left than if you had kept the real estate under your own name.
You don't have to declare anything to your home country, no tax return, they don't even know you're rich. You're properly gone, the risk of anybody bothering you is much lower.
Furthermore, but this is a totally separate issue, some countries have anti-avoidance rules for moving to low-tax territories.
They may still tax some or all of your income if you move to a low-tax country like Panama, either in general (then getting rid of the property won't help you), or if you keep real estate, even if it is rented out. This is something you really have to check.
And finally, some countries have anti-avoidance rules where payments made to businesses from Panama (and your transparent US LLC would count as such) would not be deductible, or they would have to withhold some tax. But this is only relevant for B2B. For B2C this doesn't matter, as B2C transactions wouldn't be tax-deductible anyway.
Oh, and also remember you have to pay VAT if you sell to EU consumers.