I have 9 domains (6 of which have websites) which are currently all hosted on individual hosting packages with www.siteground.com. I have recently purchased the "hosting plus" package and require all domains and sites to be transferred over to this shared hosting.
The websites need to be backed up and then transferred and pointed to the new hosting (also in Siteground).
The instructions provided by Siteground support are as follows:-
1) Use the tutorial to create a back up of each website
2) Download back ups on your local computer - Here you are: www.siteground.com/tutorials/cpanel/backup.htm
3) Set up addon slots for each website under the plus packagesiteground.com/tutorials/getting_started/extras_addon_domain.htm
4) Upload each website under its addon folder
5) You can use the same tool in the CPanel to restore back ups
6) All set
Experience and best price (fixed) will be the primary factors in choosing the contractor.