The Center for Research in Security Prices from the University of Chicago Booth School of Business has thorough tables and graphs with the properties of stock returns from 1926 to today.
You may want to particularly look at the graph "Investing for Long Term" that address your question of how many year one can be in the red.
Over a 5-year period the probability of losing money in stock markets is 12.2%. That is, randomly buying and selling at any 5-year period between 1926 to 2018, 12.2% of those draws you will lose money.
CSRP: Probability of losing money in the stock market: the importance of long-term perspective
This probability drops to 5.5% over a 8-year period. Hence, if you buy today and wait more than 8 years, based on past probabilities, there is a 5.5% change that in the next 8 year you will lose money.
The annual nominal rate of return between 1926 to today for stocks in the USA is 10%. This is a nominal rate. This implies that the equity premium, that is, the difference between equity return and risk-free assets, is between 4%-5% (see Eugene Fama & Kenneth French 2002, https://onlinelibrary.wiley.com/doi/full/10.1111/1540-6261.00437).
Though bear in minds that stock prices are highly volatile and that means that the equity premium is highly volatility. A VIX is a proxy for the equity premium, if the VIX moves, it is likely that the equity premium is moving as much (see Martin 2017, https://academic.oup.com/qje/article/132/1/367/2724543 )
CSRP: Table with historical compounded annual nominal returns for different portfolios