The Problem: Building Two Sides of a Marketplace with Manual Lists

Seth DeHart wanted to build a community where startup founders could learn sales. But he had a chicken-and-egg problem. “I needed founders to build the community, and I needed sponsors to make it sustainable. Couldn’t solve one without the other.”

Manual prospecting killed momentum. Online searches, copying profiles, guessing email formats. “I’d spend 6–8 hours building a founder list. Then another 4–5 hours finding sponsor contacts. Half the emails bounced.”

The numbers were brutal:

• Bounce rate: 40%
• Connect rate: ~5% (office numbers went to assistants)
• Month two results: 47 community members, zero sponsors
• “At this pace, I’d run out of runway before hitting critical mass. I needed both sides moving in parallel, but I was one person doing everything manually.”

The Fix: Two Campaigns, Same Platform, 20 Minutes Total

Seth found Prospeo. “I could build a list of 500 founders in 10 minutes, then switch and build 300 marketing contacts at SaaS tools in another 10 minutes. Same platform, different audiences.”

Three things changed:

• Targeting precision: Founders at 0–20 employee B2B SaaS companies for the community. Marketing directors at 50–200 employee tools for sponsors. Both lists built in minutes.
• Mobile numbers: Connect rate jumped from 5% to 22%. “I called people on their cells. Suddenly I was having 15–20 conversations per week instead of 3–4.”
• Verified emails: Bounce rate dropped from 40% to under 5%. “My domain recovered in three weeks. I could send at volume without getting blacklisted.”
• The workflow flipped. “Monday mornings, 20 minutes to build both lists. Rest of the week was actual conversations. Before, half my week was list building.”

The Results: 1,000 Founders, 5 Sponsors, One Person

Community growth:

• Month 1: 47 members
• Month 6: 1,000 members
• Weekly joins: 8–12 → 40–50

Sponsors

• Paid sponsors: 0 → 5
• Average deal: $3,500/month

Efficiency

• List building time: 15+ hrs/week → 2–3 hrs/week
• Connect rate: 5% → 22%
• Bounce rate: 40% → under 5%
• “The dual-campaign approach only worked because I could build both audiences fast,” Seth says. “Prospeo let me run two outbound motions in parallel without burning out.”

What’s Next

Founder Led Sales now has consistent growth on both sides. “I’m scaling to 10 sponsor deals by Q1. The infrastructure is built. I know exactly which filters work.”

Seth’s testing new segments. “I built a 600-person healthcare tech founder list in 30 minutes yesterday. Before, that would’ve taken a week. Now I can experiment fast.”

His advice to community builders: “If you’re building two-sided anything, you can’t manually prospect both sides. The difference between 47 members and 1,000 isn’t working 20× harder. It’s having data that connects you to the right people on both sides, fast enough to test what works.”