(concurring). Plaintiffs’ proofs on the issues of exclusion of mobile-home developments from the township and on whether the "agricultural-residential” zoning of their 113 acre parcel of land permits a reasonable use of the parcel were largely conclusory and do not adequately support rezoning to mobile-home use.
I
The parcels in the township designated for mo*446bile-home use1 had not, at the time of the hearing, been developed. There was, however, no substantial evidence that they could not or would not be so developed.2 Even if it is a reasonable inference that those parcels would have been developed with mobile home parks if that was feasible, the trier of fact was not obliged to draw that inference or to conclude that mobile-home parks had in effect been excluded from the township.
II
The proofs on the issue of the reasonableness of the present zoning were lacking in specificity.
Witnesses for the plaintiffs expressed the opinion that because of soil conditions and other circumstances the land could not profitably be farmed.
Plaintiffs’ proofs were principally directed to the feasibility of developing the parcel for single family use. The zoning ordinance requires large lots (130 foot frontage, 30,000 square feet)3 with attendant increased per lot improvement cost. The cost of the sewage treatment plant necessitated by the soil conditions was $70,000.
An expert witness testified for the plaintiffs that "[considering the cost of providing sewage treatment, the cost of records [presumably "roads”] and *447utilities, development costs, profit and overhead, the lots would have to retail for just under $6,000, and in my opinion in this location [single-family lots] would not sell for that money”; the market value of comparable lots in the area ranged from $4,000 to $5,500 per lot.4
There were no specific proofs, however, concerning the cost of platting, roads, storm sewers, a water system or wells, sewer and water lines or sales costs,5 nor was there any evidence concerning the time required to construct these improvements and to sell the lots or the availability and cost of financing during the construction and sales periods.
There is reason to believe — taking into consideration all such costs, the absence of established consumer demand,6 and the prospect that the time required to improve and sell the lots might be unduly extended because of adverse construction or market conditions — that no prudent investor would undertake the improvements required to create large single-family lots at this location. Without specific proofs, however, the trier of fact was not obliged to so find.
Ill
This case was fully briefed in this Court by the plaintiffs and the defendant before Sabo v Monroe Township, 394 Mich 531; 232 NW2d 584 (1975), *448and the companion cases7 were decided. No supplemental briefs were filed. Sabo was not adverted to during oral argument. .
The circuit court hearing was held before either Kropf8 or Sabo. Since a verdict was directed for the defendant township following the conclusion of plaintiffs’ proofs, the defendant has had no opportunity to offer proofs on the reasonableness of the proposed use; we could not properly consider that question on a one-sided record.
The majority improperly raises the Sabo issue sua sponte, an issue not raised at the trial level, in the Court of Appeals, or in briefs or during oral argument in this Court, and irrelevant to the majority’s disposition.
IV
In fairness to the plaintiffs,9 and in recognition of the uncertainty of zoning jurisprudence, our judgment of affirmance should be without prejudice to further proceedings. While the plaintiffs’ proofs are not adequate, they tend to establish that the township has effectively excluded mobile-home developments, farming is not economically feasible, the improvidence of developing this land for single-family residential purposes and that a mobile-home park might be compatible with surrounding uses and orderly development of the community.
Kavanagh, C. J., concurred with Levin, J.An 80 acre parcel was "rezoned”, by the circuit court in another proceeding, for this use. A 600-800 acre tract was shown in a future land use plan as available for this use, but that designation had not been reflected in the zoning ordinance.
The only evidence tending to show that those parcels would not be so developed was that they were located some distance from paved roads.
If an approved community sewer or central water system were to be installed, the minimum requirements would be 100 foot frontage and 20,000 square feet. The area was not served by a community sewer or water system.
The evidence was that 70 lots could be developed under the ordinance on plaintiffs’ parcel.
For example, advertising, real estate commissions, title insurance, transfer taxes.
There was no evidence of a successful single-family development in the area. It appears that the parcel is surrounded by undeveloped land, much of it devoted to farm use.
Smookler v Wheatfield Township, 394 Mich 574; 232 NW2d 616 (1975), and Nickola v Grand Blanc Township, 394 Mich 589; 232 NW2d 604 (1975).
Kropf v Sterling Heights, 391 Mich 139; 215 NW2d 179 (1974).
It would appear that plaintiffs have had no economic return from this land during this prolonged litigation. The agricultural rental value, at the time of hearing, covered only the real estate taxes.