Should web development consulting firms try to avoid targeting startups as clients? One of the key issues with startups is funding (most don't have any) and the ones that have raised a small seed, don't have enough to hire a good consulting firm to do their development.
A lot of startups have actually raised a lot of money and can pay for this kind of thing, and many others had put enough in savings to pay for costs like this.
I'd say that if a startup is approaching your consulting firm, they probably already know they're going to need money to pay you. I wouldn't ignore them just because they are a startup.
I'd simply have a short discussion with them and make sure that they know you're not OK getting equity in exchange for your work, and you're not OK getting paid later. They need to know that they'll have to pay for work in advance, or in small increments as it happens. Most will be OK with that. Most were probably expecting that.
I wouldn't ignore startups as a policy. Being a startup isn't the problem. Not having money to pay you is. Base the decision on that instead.