What is the best exit option for angel/seed investor?

Stop thinking you don't have the skills to do something. You can learn anything if you decide to, but assuming up front that you can't (forever) is dangerous. my2cents

Back when I started LinkedIn wasn't as huge as it is now. I wish it was. I didn't have a large network and those networking sessions NEVER brought me any clients. I used to go to all sorts of them hoping to get clients. There were a couple of nibbles here and there, but never anything serious. The only thing that helped was reaching out DIRECTLY to people in my target market. That meant cold calls and cold emails. I'd sell myself while thinking about their needs. Once I got a few bites I'd build good rapport by keeping in touch, asking questions, repeating back what they were saying so that they knew I was on the same page and kept my promises. If I said I'd call them back next Tuesday at 2:15 I'd do so. Eventually I built trust with them without having a network, or an insane amount of experience. Oh and the most important thing about consulting is to LISTEN. When those first clients notice that you're truly listening and you're not selling the cookie cutter solutions everyone else is trying to sell them that's when you got them hooked. You start to understand their problems, fears, and see through their eyes and not just yours. A network will help, but in the beginning just good 'ol salesmanship will get the ball rolling.

Before I get to your question, let me give you a tip: always aim settle questions of payment before the work happens. It is ten times easier to agree on a price beforehand, and having done that doesn't stop you from changing it by mutual agreement later. The problem with paying cash is pretty obvious: you don't have a lot of it. The problems with paying equity are subtler. The first one is that early-stage equity is extremely hard to value. A second is that equity transactions require a lot of paperwork. Third is that entrepreneurs tend to value their equity much higher than other people would; if not, they wouldn't be starting the company. And fourth, people like designers are rarely expert in valuing businesses or the customs of of startup equity valuation. In the past, I've both given and received equity compensation, and it's a lot more of a pain than I expected. In the future, what I think I'd try is convertible debt. That is, I'd talk with the designer and agree on a fair-market wage. E.g. 100 hours x $100/hr = $10k. The next time we take investment, the $10k turns into stock at whatever price we agree with our investors, plus a discount because he was in before the investors. Note, though, that this will increase your legal costs and your deal complexity, so I'd personally only do this for a pretty significant amount of work. And I'd only do it for somebody I trusted and respected enough to have them around for the life of my business.

The ideal way would be to hire the engineer while the project is still under development. You and the engineer should follow up with the outsourced partner in the process. This will give hold to the engineer and later more staff can be trained in upgrading or follow on versions of the product/service.

Better than a cover letter is to actually proactively DO something to help them. It'll show them not only that you've researched them, but you're passionate about the startup and worth bringing on. A man got a job at Square early on for just making them a marketing video on his own (back before they had one). Since you're a web designer, design a stellar 1-pager that's targeting their message to a particular niche. Something they could use on social media or something. If they're like most startups, they're not interested in reading cover letters. They're interested in passionate individuals who can add value to the organization.