Good advice from ajross and pg. The fact that they don't have an option plan in place suggests that it's definitely very early stages. What level of funding do they have? Especially if you're that early, you should DEFINITELY be seeking equity.
To put it in perspective, we just made our first non-founder employee - a senior developer - and we gave up 4% to get him. It's on the high side, but as a first hire and someone who we didn't want to lose, we were willing to give that up.
That said, the legal costs with creating an option plan (and registering for business in the state if it's a DE corporation) are not insignificant. Especially if they don't have much money yet, and want to spend that mostly on talent, that can be a factor here.
If they haven't done an equity round yet (i.e., valued the company), then the stock is effectively worthless (par value is probably $0.001 per share or something in that range, and normally you would see something like 5M shares authorized and outstanding). So in this scenario, an option with this strike price is effectively the same as an equity grant.
We were lucky - we're doing our initial stock purchase agreements now (we incorporated awhile back but had to redistribute some equity as involvement with co-founders changed) and we were able to include our first hire in that plan. We all have the same vesting schedule - 4 yrs prorated with a 1yr cliff - but our initial dates are a year or so earlier than his. This saved us at least 5k in legal fees.
My advice would be, like ajross and pg suggested, to negotiate what equity will be granted - even if they don't yet have the means to grant. And, if they wanted, they could also sell you shares under the same original purchase agreement (assuming they have a vesting schedule they're happy with, and they had some authorized but unissued shares).
Basically, if you want the job and like the company, take it - but if you don't negotiate the equity now (even if it can't be executed yet) then don't expect it later.