U said u have come here to attend a conference so i think u may be on tourist visa.In this case u can stay up to a maximum of 28 days only.
But if u are on visit visa and if ur sponsor is any of ur family member, then before completing one month in Qatar u have to get ur medical done and if the results are OK u can get it extended for another 5 months.That is u r eligible to stay in Qatar for 6 months from the date of arrival.Chk the exact status of ur visa if its visit or tourist.

On house visa u are not allowed to work outside but if its the visa of the owner of the company I think they can manage to employ u for office work.Its better to chk with the company itself. Regarding converting from house visa to family visa u need to chk with the company if this house visa has any limitations because I think this visa will be valid for two years and u wont be able to move anywhere. Check all the limitations and pros & cons of this visa and then take a descision.

All the best