@Jake S., this is a great topic. As noted, there is no one size fits all option. But that being said, there are many risks that need to be balanced:
- Sponsor Risk
- Asset class (multifamily, industrial, etc)
- Position style: debt, equity, pref equity
- Risk Profile of the asset: core, core +, value-add, development
- Hold period
- Geography
- Debt type/maturity
To name a few. And then you get into broader portfolio theory: how much of that net worth should be tied to real estate, versus stocks, bonds, private equity, venture capital, etc.
If the last three years of these forums are any indication, there are a lot of people that are over concentrated in value-add multifamily. While I still buy into this business model personally as an LP, as a whole my value-add multifamily LP positions are about 10% of my net worth. Another 20% is in my retirement fund. Then I have retail investments, a couple directly owned rentals, cash available for flips, my primary residence, 529 accounts in mutual funds, etc.
The challenge with true diversification is: it is safe. Safe means steady and safe means lower returns. Most people don't want to acknowledge this. Most investors are chasing return, which is fine, but as we are seeing in real time, it means you are going to hit some volatile markets and maybe lose money. Nothing that pencils to 20% IRRs isn't without risk. As discusses on @Scott Trench's thread about "pref equity", there are always risks. If the asset class isn't the risk, the business plan is, or the asset itself, or the financing level. And if there isn't risk, the return will be much lower. Econ 101: there is no such thing as a free lunch.
Look at most 9 figure net worth people: they are not chasing 20% returns. Typically, they want a safe 4-6% over the long term. Same with pensions and endowments, at least in real estate. But as you note, if you want a $1mm net worth to grow to $10mm in the next 10 years, you are going to be taking on a good amount of risk to get there. Some will win, some will lose, and clearly track record is only as good as the market it was produced in.