Cons: Expensive to maintain - can push tenants away who don't have the extra money and you certainly don't want pool cleaning coming out of your monthly rent. 

If I have a PM to take over management work, the extra profit of multi-family over single family goes to PM's income.

As long as you have extra reserves given the volatile nature of the world right now, I would continue to invest.

As a result, for the new house I would buy, they want to charge an extra 25% of my current mortgage as a down payment on the new house, in addition to the 20% down....Do you know anything about this?

Your capital is more protected from the extra doors and your cash flow can grow exponentially.

I would not replace the carpeting, can it be glued down until they get the dog and all the extra people out?

I also had a renter that received the $1,200 stimulus and $600 extra a week on top of her regular unemployment.

They will charge 8 to 10% based on property condition and the local market.After you remove all the extra expenses from your balance sheet, this deal might be tenable. 

2) Would it imply extra expenses for being a non US citizen on the purchasing and owning of a property ? 

You should be at 70% to 75% after everything. this way you DONT have a bunch of cash left in the deal.Also, about $200 per month: Once you get more deals, you put extra money into getting 1 or 2 paid off.