Which form of investment is characterized by a flexible structure where investors can enter and exit?

Open-ended funds are characterized by their flexible structure, which allows investors to buy and sell shares without restrictions, facilitating easy entry and exit. This type of fund does not have a fixed number of shares; instead, new shares are created when investors purchase them, and shares are redeemed when investors sell. This continuous issuance and redemption process makes open-ended funds highly liquid compared to other forms of investment.

Closed-ended funds, in contrast, have a fixed number of shares that are traded on a stock exchange, meaning investors can only buy or sell shares at market prices, which may differ from the fund's net asset value. Private equity funds generally require longer commitment periods, often locking investors' capital for several years, making them less flexible in terms of investor entry and exit. Real estate investment trusts (REITs) can provide liquidity similar to open-ended funds but are structured specifically to invest in real estate and do not offer the same level of flexibility regarding share transactions as open-ended funds. Therefore, the open-ended fund's structure is what distinctly provides the flexibility for investors to easily enter and exit.