"The traditional investment vehicles have been bonds or other conservative investments, but the yields aren't enough to give people the retirement that they envision for themselves," he says. "Net lease has a higher return than bonds and is a little bit of a different risk profile. But if you invested through REITs or an ETF, it [net lease] is a better yielding vehicle. So, I think that's going to keep cap rates from moving too far up."

The number of net leases properties on the market stayed remarkably consistent year over year. Last year at this time, there were 5,235 properties available. Now, 5,230 properties are on the market.

"There just seem to be less sellers in the market today," Blankstein says. "We're in year eight of the recovery and a lot of the people who were turning in a quick profit have done so at this point. So, I think it has stabilized from a supply-demand imbalance."

Even with a stabilized supply-demand situation, Blankstein sees some net lease investors taking on more risk with cap rates at such low levels. As an example, he points to the narrowing spread of 30 basis points between primary, secondary and tertiary markets. Traditionally, he says spreads have been 60 to 80 basis points.

"I think people are overpaying for some of the secondary and tertiary markets at this point," Blankstein says. "With the smaller spreads, I'd rather buy primary markets at this point in the cycle. You might as well choose the best market because you're not really getting paid enough [to take the risk]."

If investors are staying in primary markets, they have been chasing speculative credits. "You see people chasing secondary names like Rite-Aid, Tesla and Applebee's," Blankstein says. "They are high yield, but they are still in primary markets and you're taking some credit risk."