The table below provides the requirements when the security property consists of more than one parcel of real estate.
Multiple Parcels Requirements
Each parcel must be conveyed in its entirety.
Parcels must be adjoined to the other, unless they comply with the following exception. Parcels that otherwise would be adjoined, but are divided by a road, are acceptable if the parcel without a residence is a non-buildable lot (for example, waterfront properties where the parcel without the residence provides access to the water). Evidence that the lot is non-buildable must be included in the loan file.
Each parcel must have the same basic zoning (for example, residential, agricultural).
The entire property may contain only one dwelling unit. Limited additional non-residential improvements, such as a garage, are acceptable. For example, the adjoining parcel may not have an additional dwelling unit. An improvement that has been built across lot lines is acceptable. For example, a home built across both parcels where the lot line runs under the home is acceptable.
The mortgage must be a valid first lien that covers each parcel.
https://www.google.com/search?q=duplex+conventional+loan&rlz=1C1GCEA_en&oq=duplex+conventional+loan&aqs=chrome..69i57j0i10i22i30j0i22i30j0i390l3.5377j0j1&sourceid=chrome&ie=UTF-8
https://selling-guide.fanniemae.com/Selling-Guide/Origination-thru-Closing/Subpart-B2-Eligibility/Chapter-B2-3-Property-Eligibility/1032991541/B2-3-04-Special-Property-Eligibility-Considerations-12-16-2020.htm#Multiple.20Parcels
所以可能可以跟本地小银行合作credit union做portfolio loan，但是不知道会不会比两个conventional loan划算。
Number of Units
Fannie Mae purchases or securitizes first-lien mortgages that are secured by residential properties when the dwelling consists of one to four units.
https://selling-guide.fanniemae.com/Selling-Guide/Origination-thru-Closing/Subpart-B2-Eligibility/Chapter-B2-3-Property-Eligibility/1032991721/B2-3-01-General-Property-Eligibility-09-02-2020.htm#Number.20of.20Units
Multiple Parcels
The table below provides the requirements when the security property consists of more than one parcel of real estate.
不过找一家公司做两个贷款应该没问题。还可以用conventional loan。
well permits了，都是buildable的，虽然我不会去这样去建房子。
septic tank and well are not dwellings.