Hi. First of all, I have a few questions I would like to ask;
1) What is it exactly that you need? is it a mockup for a landing page for a website (which is, of course, responsive)? Or a mockup of a complete website?
2) Is it mockups for an IOS, and Android app as well, or 'just' a responsive/mobile friendly website?
3) Do you need both website(/app) and a logo design or do you want to start with of the two?
4) A mockup is defined as a design of a website/app. However, you state that knowledge of HTML is a must? You do not need HTML skills to design a mockup, so I wondered if you really need a complete site; designed and coded?
Please know that the bid and time range of delivery is both estimated - and will heavily depend on what it is you actually need.
Best,
Kevin