Filing with the Colorado Secretary of State takes an afternoon. Choosing the entity is the real work of business formation, and writing the agreement that actually runs it is the part that protects you.
The short answer
What an LLC does
An LLC can keep business debts and many lawsuits away from your personal savings, if you treat the company as its own person. That means a separate bank account, contracts in the company name, and enough money in the company to operate. A company that is only a name on paper is a weak shield.
The operating agreement says who owns the company, who decides, and what happens if an owner dies, divorces, or wants out. The state filing does not do that work.
Where an S corporation fits
An S corporation is usually a tax status an LLC or a corporation elects with the IRS. In some cases it changes how self-employment tax applies to profits, after the owner takes a reasonable salary. It also adds payroll, a separate tax return, and stricter ownership rules. It is not automatically better. A CPA should run the numbers before you elect it.
One company or several
A single LLC can own one rental or several. Separate LLCs can isolate one property's risk from the others, at the cost of more accounts, filings, and tax work. The right number depends on how many properties you have, how they are financed, and whether you will keep them.
Connect it to your estate plan
The operating agreement and your will or trust should describe the same outcome. If they conflict, the people you love may not be able to manage or sell the business. Membership can be left to a trust. Someone should also have authority to act if you cannot, through the agreement and a financial power of attorney.
This guide is general information, not legal advice, and reading it does not create an attorney-client relationship. Laws change, and every family is different.