I and going to the USA on a VWP and have been offered a job. Can my employer get my work visa while I am in the USA?
No. Visa waiver program visitors may not change their status in the US except if they are doing so as an immediate family member of a US citizen.
Questions about work permits belong on Expatriates, so please ask there if you want more detailed information about the kinds of work visas that may be suitable for you. The most common of these are scarce, so it could take a couple of years to get one.