//get the business account record type
RecordType NotPersonAccountRecordType = [select Id, Name, SobjectType,
         IsPersonType from RecordType where SobjectType='Account'
         and IsPersonType=False];

// get 1 existing account
Contact c = [select id, AccountId, FirstName, LastName, Cris_Id__c from Contact where IsPersonAccount = false Limit 1];


// create a new account and set the record type to business account
Account newAccount = new Account();
newAccount.Name='' + c.LastName;
newAccount.RecordTypeId = NotPersonAccountRecordType.Id;
insert newAccount;


//get the person account record type
recordType personaccountrecordtype = [select Id, Name, SobjectType,
         IsPersonType from RecordType where SobjectType='Account'
         and IsPersonType=True];

// update the existing contact's account to new account
c.AccountId = newAccount.Id;
update c;


// now get it again and update the firstname and lastname, change the record type to person account
newAccount = [select id,lastName, Firstname, RecordTypeId from Account where Id =: newAccount.Id];
newAccount.RecordTypeId = personaccountrecordtype.Id;
newAccount.LastName=c.LastName;
newAccount.FirstName=c.FirstName;   
update newAccount;