Is buying stocks to retire, instead of buying several houses, equally feasible?

For most people a properly diversified stock market investment is actually better than buying 4 houses:

• you can start investing with small amounts of money every month
• a house is a huge clump investment. This is the exact opposite of a diversified investment. It does not matter if you are a company with thousands of units but if you only have 1 or 2 houses this is an issue
• buying houses for investment tends to clump risk even more as you are likely to buy something in the region you live. If that region experiences a long term economic downturn, all your properties lose value
• The calculation of rent=1/3 of income ==> 3 units make a living is discarding maintenance: the heating breaks, the roof leaks after some decades and so on. This is something you need to pay from your rental income. Management of any sorts also draws on this money
• It is even more flawed as you likely won't be able to afford 3 rental houses at your standard. You are getting 1/3 of someone elses lower income for each unit.
• Timing issues: Both with buying and selling you have timing issues if you only trading in huge chunks of money. Get it wrong and you will lose a lot of money. Selling shares for 1000$ per month is so much easier than selling a 1000$ share of your house

That said there is nothing wrong with owning a house for yourself. There are other benefits to it than just saving on rent. However, when talking about buying a house for investment, things should be critically evaluated

and always worry about the maintenance etc...

I have to say IMO this is just a common myth.

You have a service that handles the renting, and once in a blue moon you make a two-minute call to have someone install a new dishwasher or whatever.

It's certainly true that many folks agree with you, "renting is a big chore", I have always found that mystifying. Sometimes on this list someone will comment that they don't want to own a house to live in, they'd rather just rent since home ownership is "so much work". Again I just find this mystifying, the entire process of buying, owning, and ultimately selling a house involves maybe 3 signatures, it's nothing.

But to each his own.

income ...

Unfortunately one makes very little income from rental houses OR from stocks.

The reason to do either is

capital gains ...

Regarding stocks, it's common that over say 20 years you can get a substantial (say 3, 4, 5x) capital gain. Look at the second graph here https://money.stackexchange.com/a/135187/41786

Regarding stocks, it's common that over say 20 years you can get a substantial drop (50, 70%). Look at the first graph here https://money.stackexchange.com/a/135187/41786

With housing markets, it is extremely rare that they drop over decade lengths. It is rare but not unknown that they stay flat. It is usual that they go up. And it is relatively common that they go up very dramatically. Here's an extreme example like San Francisco, https://money.stackexchange.com/a/133985/41786

You could look at the difference like this. Over 20 or 30 years...

• over 20 years, stock markets often go straight down, and often go straight up.

• over 20 years, real estate usually goes up, occasionally is flat (and only in extremely rare cases, like Detroit, down)

Regarding income, with rentals you know exactly how much you will get to the dollar, week in, week out, year in, year out, with increases continually over the years. With stocks, income is probably "a bit more" than rentals but is highly erratic.

solid companies ...

This is a dangerous myth, survivorship bias, as often discussed on this site. It's impossible to know which companies will be "solid" from today on. https://money.stackexchange.com/a/127868/41786

It is very hard to "stock pick" and beat just an ordinary index fund.

protect against big market drop...

If you do go with "stock market" it does seem very wise to, as you say, spend some on this type of protection.