Jason Schultz and Scott Piercy are tied one stroke further back at minus-6. Brian Wilson, Bobby Gage, Bubba Watson and Roland Thatcher are tied for sixth at 5-under-par 67.
The three leaders each began their rounds on the back nine at Willow Creek Country Club. Porter and Freeman had similar rounds of five birdies and one eagle.
Porter caught fire early on in his round. He birdied the par-5 12th, his third. He followed that up with an eagle at the par-4 13th when he holed a sand-wedge from 105 yards out. He quickly moved to 4 under for his round with a birdie at the next.
The 37-year-old capped his opening nine with a birdie at the 18th. Around the turn, he birdied the par-5 third. He grabbed a share of the first-round lead thanks to a birdie at the par-3 seventh.
'I had a couple of really good opportunities that I wasn't able to take advantage of,' said Porter, who still posted his best round of the season. 'I had some good things happen to me, so it balanced out, I guess.'
Porter climbed to the top of the leaderboard using new clubs that he first touched last week.
'I hit them for the first time last Friday at home,' Porter said. 'My swing immediately felt better. I didn't know what to expect. I hit enough good shots to play well.'
Freeman kicked off his round with back-to-back birdies from the 12th. He moved to minus-4 with a chip-in eagle on the par-5 17th. Around the turn, he picked up his third birdie at the fifth before closing out his round with consecutive birdies from the par-4 eighth.
'My confidence has been high because of my ball-striking,' said Freeman, who has struggled with the putter recently. 'If the putter comes around I'll be okay. I've been changing putters every week. I gave this one to my wife and she told me to take it and use it this week. If this doesn't work, I've got to go to the broom.'
Gutschewski opened with birdies on his first two par-5s, Nos. 10 and 12. However, his momentum was briefly halted with a bogey at the 13th. He finished his opening nine in style with an eagle at the 17th and a birdie at the next.
On the front side, Gutschewski could not birdie the par-5 first, but he did birdie the par-5 third to move to 5 under on the par-5s. He grabbed a share of the lead with back-to-back birdies from the par-4 sixth.
'You have to make birdies. I don't have much of a choice,' said Gutschewski, who is 60 under par in his last 17 rounds. 'If I don't make birdies, I won't be playing next week.'
Gutschewski, who averaged 340 yards off the tee Thursday, has managed to play in five straight events with no status on tour. He received a sponsor's exemption to his first event and has finished in the top-25 of the last four events to gain entry into the following week's field.
'I'm playing out here on good golf courses against quality competition and if I don't finish in the top 25, I can't play,' Gutschewski said. 'If I say I'm not surprised to be playing well, I'll come across as arrogant, but I don't think you can really do it if you don't expect it.'
Joe Ogilvie, a two-time winner on the Nationwide Tour this season, heads a list of 13 players tied for 10th at 4-under-par 68. Joining Ogilvie at minus-4 are Shane Bertsch, D.J. Brigman, Daniel Chopra, Keoke Cotner, Stephen Gangluff, Hunter Haas, Ryuji Imada, Zach Johnson, Jerry Smith, Kyle Thompson, Tommy Tolles and Brett Wetterich.